diff --git a/compiler/src/dmd/funcsem.d b/compiler/src/dmd/funcsem.d
index a02d9b7781..3b7b3097c9 100644
--- a/compiler/src/dmd/funcsem.d
+++ b/compiler/src/dmd/funcsem.d
@@ -1763,13 +1763,17 @@ FuncDeclaration resolveFuncCall(Loc loc, Scope* sc, Dsymbol s,
             if (!od && !td.overnext)
             {
                 .error(loc, "%s `%s` is not callable using argument types `!(%s)%s`",
-                   td.kind(), td.ident.toChars(), tiargsBuf.peekChars(), fargsBuf.peekChars());
+                    td.kind(), td.ident.toChars(), tiargsBuf.peekChars(), fargsBuf.peekChars());
+
+                checkNamedArgErrorAndReport(td, argumentList, loc);
             }
             else
             {
                 .error(loc, "none of the overloads of %s `%s.%s` are callable using argument types `!(%s)%s`",
-                   td.kind(), td.parent.toPrettyChars(), td.ident.toChars(),
-                   tiargsBuf.peekChars(), fargsBuf.peekChars());
+                    td.kind(), td.parent.toPrettyChars(), td.ident.toChars(),
+                    tiargsBuf.peekChars(), fargsBuf.peekChars());
+
+                checkNamedArgErrorAndReport(td, argumentList, loc);
             }
 
 
@@ -1789,7 +1793,9 @@ FuncDeclaration resolveFuncCall(Loc loc, Scope* sc, Dsymbol s,
     if (od)
     {
         .error(loc, "none of the overloads of `%s` are callable using argument types `!(%s)%s`",
-               od.ident.toChars(), tiargsBuf.peekChars(), fargsBuf.peekChars());
+            od.ident.toChars(), tiargsBuf.peekChars(), fargsBuf.peekChars());
+
+        checkNamedArgErrorAndReportOverload(od, argumentList, loc);
         if (!global.gag || global.params.v.showGaggedErrors)
             printCandidates(loc, od, sc.isDeprecated());
         return null;
@@ -1920,6 +1926,62 @@ FuncDeclaration resolveFuncCall(Loc loc, Scope* sc, Dsymbol s,
     return null;
 }
 
+/********************************************************
+ * Check for named argument errors in template declarations and report them.
+ * Params:
+ *      td = template declaration to check
+ *      argumentList = arguments to check
+ *      loc = location for error reporting
+ */
+private void checkNamedArgErrorAndReport(TemplateDeclaration td, ArgumentList argumentList, Loc loc)
+{
+    if (!argumentList.hasNames())
+        return;
+
+    auto tf = td.onemember ? td.onemember.isFuncDeclaration() : null;
+    if (tf && tf.type && tf.type.ty == Tfunction)
+    {
+        OutBuffer buf;
+        auto resolvedArgs = tf.type.isTypeFunction().resolveNamedArgs(argumentList, &buf);
+        if (!resolvedArgs && buf.length)
+            .errorSupplemental(loc, "%s", buf.peekChars());
+    }
+}
+
+/******************************************
+ * Check for named argument errors in overload sets and report them.
+ * Params:
+ *      od = overload declaration to check
+ *      argumentList = arguments to check
+ *      loc = location for error report
+ */
+private void checkNamedArgErrorAndReportOverload(Dsymbol od, ArgumentList argumentList, Loc loc)
+{
+    if (!argumentList.hasNames())
+        return;
+
+    FuncDeclaration tf = null;
+    overloadApply(od, (Dsymbol s) {
+        if (!tf)
+        {
+            if (auto fd = s.isFuncDeclaration())
+                tf = fd;
+            else if (auto td = s.isTemplateDeclaration())
+                if (td.onemember)
+                    tf = td.onemember.isFuncDeclaration();
+        }
+        return 0;
+    });
+
+    if (tf && tf.type && tf.type.ty == Tfunction)
+    {
+        OutBuffer buf;
+        auto resolvedArgs = tf.type.isTypeFunction().resolveNamedArgs(argumentList, &buf);
+        if (!resolvedArgs && buf.length)
+            .errorSupplemental(loc, "%s", buf.peekChars());
+    }
+}
+
 /*******************************************
  * Prints template and function overload candidates as supplemental errors.
  * Params:
diff --git a/compiler/test/fail_compilation/fix21042.d b/compiler/test/fail_compilation/fix21042.d
new file mode 100644
index 0000000000..b2b224e519
--- /dev/null
+++ b/compiler/test/fail_compilation/fix21042.d
@@ -0,0 +1,15 @@
+/*
+TEST_OUTPUT:
+---
+fail_compilation/fix21042.d(14): Error: template `gun` is not callable using argument types `!()(int)`
+fail_compilation/fix21042.d(14):        no parameter named `x`
+fail_compilation/fix21042.d(10):        Candidate is: `gun(T)(T a)`
+---
+*/
+
+void gun(T)(T a) {}
+
+void main()
+{
+	gun(x: 1); // (no explanation) --> (no parameter named `x`)
+}
diff --git a/compiler/test/fail_compilation/named_arguments_error.d b/compiler/test/fail_compilation/named_arguments_error.d
index 125ebcc926..761e1d4c78 100644
--- a/compiler/test/fail_compilation/named_arguments_error.d
+++ b/compiler/test/fail_compilation/named_arguments_error.d
@@ -1,26 +1,27 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/named_arguments_error.d(37): Error: function `f` is not callable using argument types `(int, int, int)`
-fail_compilation/named_arguments_error.d(37):        parameter `x` assigned twice
-fail_compilation/named_arguments_error.d(31):        `named_arguments_error.f(int x, int y, int z)` declared here
 fail_compilation/named_arguments_error.d(38): Error: function `f` is not callable using argument types `(int, int, int)`
-fail_compilation/named_arguments_error.d(38):        argument `4` goes past end of parameter list
-fail_compilation/named_arguments_error.d(31):        `named_arguments_error.f(int x, int y, int z)` declared here
+fail_compilation/named_arguments_error.d(38):        parameter `x` assigned twice
+fail_compilation/named_arguments_error.d(32):        `named_arguments_error.f(int x, int y, int z)` declared here
 fail_compilation/named_arguments_error.d(39): Error: function `f` is not callable using argument types `(int, int, int)`
-fail_compilation/named_arguments_error.d(39):        parameter `y` assigned twice
-fail_compilation/named_arguments_error.d(31):        `named_arguments_error.f(int x, int y, int z)` declared here
+fail_compilation/named_arguments_error.d(39):        argument `4` goes past end of parameter list
+fail_compilation/named_arguments_error.d(32):        `named_arguments_error.f(int x, int y, int z)` declared here
 fail_compilation/named_arguments_error.d(40): Error: function `f` is not callable using argument types `(int, int, int)`
-fail_compilation/named_arguments_error.d(40):        no parameter named `a`
-fail_compilation/named_arguments_error.d(31):        `named_arguments_error.f(int x, int y, int z)` declared here
-fail_compilation/named_arguments_error.d(41): Error: function `g` is not callable using argument types `(int, int)`
-fail_compilation/named_arguments_error.d(41):        missing argument for parameter #1: `int x`
-fail_compilation/named_arguments_error.d(33):        `named_arguments_error.g(int x, int y, int z = 3)` declared here
-fail_compilation/named_arguments_error.d(43): Error: no named argument `element` allowed for array dimension
-fail_compilation/named_arguments_error.d(44): Error: no named argument `number` allowed for scalar
-fail_compilation/named_arguments_error.d(45): Error: cannot implicitly convert expression `g(x: 3, y: 4, z: 5)` of type `int` to `string`
-fail_compilation/named_arguments_error.d(46): Error: template `tempfun` is not callable using argument types `!()(int, int)`
-fail_compilation/named_arguments_error.d(49):        Candidate is: `tempfun(T, U)(T t, U u)`
+fail_compilation/named_arguments_error.d(40):        parameter `y` assigned twice
+fail_compilation/named_arguments_error.d(32):        `named_arguments_error.f(int x, int y, int z)` declared here
+fail_compilation/named_arguments_error.d(41): Error: function `f` is not callable using argument types `(int, int, int)`
+fail_compilation/named_arguments_error.d(41):        no parameter named `a`
+fail_compilation/named_arguments_error.d(32):        `named_arguments_error.f(int x, int y, int z)` declared here
+fail_compilation/named_arguments_error.d(42): Error: function `g` is not callable using argument types `(int, int)`
+fail_compilation/named_arguments_error.d(42):        missing argument for parameter #1: `int x`
+fail_compilation/named_arguments_error.d(34):        `named_arguments_error.g(int x, int y, int z = 3)` declared here
+fail_compilation/named_arguments_error.d(44): Error: no named argument `element` allowed for array dimension
+fail_compilation/named_arguments_error.d(45): Error: no named argument `number` allowed for scalar
+fail_compilation/named_arguments_error.d(46): Error: cannot implicitly convert expression `g(x: 3, y: 4, z: 5)` of type `int` to `string`
+fail_compilation/named_arguments_error.d(47): Error: template `tempfun` is not callable using argument types `!()(int, int)`
+fail_compilation/named_arguments_error.d(47):        argument `1` goes past end of parameter list
+fail_compilation/named_arguments_error.d(50):        Candidate is: `tempfun(T, U)(T t, U u)`
 ---
 */
 
diff --git a/compiler/test/fail_compilation/named_arguments_ifti_error.d b/compiler/test/fail_compilation/named_arguments_ifti_error.d
index 6d8a70a2c4..a73fd3cb2e 100644
--- a/compiler/test/fail_compilation/named_arguments_ifti_error.d
+++ b/compiler/test/fail_compilation/named_arguments_ifti_error.d
@@ -1,12 +1,15 @@
 /*
 TEST_OUTPUT:
 ---
-fail_compilation/named_arguments_ifti_error.d(17): Error: template `f` is not callable using argument types `!()(int, int)`
-fail_compilation/named_arguments_ifti_error.d(13):        Candidate is: `f(T, U)(T x, U y)`
-fail_compilation/named_arguments_ifti_error.d(18): Error: template `f` is not callable using argument types `!()(int, int)`
-fail_compilation/named_arguments_ifti_error.d(13):        Candidate is: `f(T, U)(T x, U y)`
-fail_compilation/named_arguments_ifti_error.d(19): Error: template `f` is not callable using argument types `!()(int)`
-fail_compilation/named_arguments_ifti_error.d(13):        Candidate is: `f(T, U)(T x, U y)`
+fail_compilation/named_arguments_ifti_error.d(20): Error: template `f` is not callable using argument types `!()(int, int)`
+fail_compilation/named_arguments_ifti_error.d(20):        parameter `x` assigned twice
+fail_compilation/named_arguments_ifti_error.d(16):        Candidate is: `f(T, U)(T x, U y)`
+fail_compilation/named_arguments_ifti_error.d(21): Error: template `f` is not callable using argument types `!()(int, int)`
+fail_compilation/named_arguments_ifti_error.d(21):        argument `3` goes past end of parameter list
+fail_compilation/named_arguments_ifti_error.d(16):        Candidate is: `f(T, U)(T x, U y)`
+fail_compilation/named_arguments_ifti_error.d(22): Error: template `f` is not callable using argument types `!()(int)`
+fail_compilation/named_arguments_ifti_error.d(22):        missing argument for parameter #1: `T x`
+fail_compilation/named_arguments_ifti_error.d(16):        Candidate is: `f(T, U)(T x, U y)`
 ---
 */