diff --git a/gen/llvmhelpers.cpp b/gen/llvmhelpers.cpp
index 72f06f92dc..dd0400eab9 100644
--- a/gen/llvmhelpers.cpp
+++ b/gen/llvmhelpers.cpp
@@ -1440,3 +1440,40 @@ IrModule * getIrModule(Module * M)
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////
+
+size_t realignOffset(size_t offset, Type* type)
+{
+    size_t alignsize = type->alignsize();
+    size_t alignedoffset = (offset + alignsize - 1) & ~(alignsize - 1);
+
+    // if the aligned offset already matches the input offset
+    // don't waste time checking things are ok!
+    if (alignedoffset == offset)
+        return alignedoffset;
+
+    // disabled since this can fail for opaques. if the check above is not in place
+    // it does so for gcx.d!!!
+    // this needs to be investigated, but I don't have time right now!
+#if 0
+    // if not, we have to make sure it agrees with what llvm thinks is the alignment
+    // sometimes this is different from what we really need (in case of unions, see #294)
+    // so if there we get different results we don't realign the offset at all and instead
+    // just return the original offset, and rely on the users to insert padding manually.
+    IF_LOG Logger::cout() << "getting alignment for type " << type->toChars()
+        << " with llvm type " << *DtoType(type) << std::endl;
+    size_t alignsize2 = gTargetData->getABITypeAlignment(DtoType(type));
+
+    if (alignsize != alignsize2)
+    {
+        assert(alignsize > alignsize2 && "this is not good, the D and LLVM "
+            "type alignments differ, but LLVM's is bigger! This will break "
+            "the type mapping algorithms");
+        // don't try and align the offset, and let the mappers pad 100% manually
+        return offset;
+    }
+#endif
+
+    return alignedoffset;
+}
+
+//////////////////////////////////////////////////////////////////////////////////////////
diff --git a/gen/llvmhelpers.h b/gen/llvmhelpers.h
index 8cc4e38cbd..391fe820b6 100644
--- a/gen/llvmhelpers.h
+++ b/gen/llvmhelpers.h
@@ -141,6 +141,10 @@ DValue* DtoInlineAsmExpr(Loc loc, FuncDeclaration* fd, Expressions* arguments);
 /// Create the IrModule if necessary and returns it.
 IrModule* getIrModule(Module* M);
 
+/// Update an offset to make sure it follows both the D and LLVM alignments.
+/// Returns the offset rounded up to the closest safely aligned offset.
+size_t realignOffset(size_t offset, Type* type);
+
 ////////////////////////////////////////////
 // gen/tocall.cpp stuff below
 ////////////////////////////////////////////
diff --git a/gen/toir.cpp b/gen/toir.cpp
index 6750475f45..66f152cf1c 100644
--- a/gen/toir.cpp
+++ b/gen/toir.cpp
@@ -2459,8 +2459,7 @@ DValue* StructLiteralExp::toElem(IRState* p)
         size_t alignedoffset = offset;
         if (!packed)
         {
-            size_t alignsize = vd->type->alignsize();
-            alignedoffset = (offset + alignsize - 1) & ~(alignsize - 1);
+            alignedoffset = realignOffset(alignedoffset, vd->type);
         }
 
         // insert explicit padding?
diff --git a/ir/irclass.cpp b/ir/irclass.cpp
index 624b06cfd9..8754744ee5 100644
--- a/ir/irclass.cpp
+++ b/ir/irclass.cpp
@@ -222,8 +222,7 @@ void IrStruct::addBaseClassInits(
         assert(vd->offset >= offset && "default fields not sorted by offset");
 
         // get next aligned offset for this type
-        size_t alignsize = vd->type->alignsize();
-        size_t alignedoffset = (offset + alignsize - 1) & ~(alignsize - 1);
+        size_t alignedoffset = realignOffset(offset, vd->type);
 
         // insert explicit padding?
         if (alignedoffset < vd->offset)
diff --git a/ir/irstruct.cpp b/ir/irstruct.cpp
index 144bad19d9..b058596c70 100644
--- a/ir/irstruct.cpp
+++ b/ir/irstruct.cpp
@@ -169,8 +169,7 @@ LLConstant * IrStruct::createStructDefaultInitializer()
         size_t alignedoffset = offset;
         if (!packed)
         {
-            size_t alignsize = vd->type->alignsize();
-            alignedoffset = (offset + alignsize - 1) & ~(alignsize - 1);
+            alignedoffset = realignOffset(alignedoffset, vd->type);
         }
 
         // insert explicit padding?
@@ -355,8 +354,7 @@ LLConstant * IrStruct::createStructInitializer(StructInitializer * si)
         size_t alignedoffset = offset;
         if (!packed)
         {
-            size_t alignsize = vd->type->alignsize();
-            alignedoffset = (offset + alignsize - 1) & ~(alignsize - 1);
+            alignedoffset = realignOffset(alignedoffset, vd->type);
         }
 
         // insert explicit padding?
diff --git a/ir/irtypeclass.cpp b/ir/irtypeclass.cpp
index 3bc9bf4a98..4ae835e8ee 100644
--- a/ir/irtypeclass.cpp
+++ b/ir/irtypeclass.cpp
@@ -9,6 +9,7 @@
 #include "gen/logger.h"
 #include "gen/tollvm.h"
 #include "gen/utils.h"
+#include "gen/llvmhelpers.h"
 #include "ir/irtypeclass.h"
 
 //////////////////////////////////////////////////////////////////////////////
@@ -143,8 +144,7 @@ void IrTypeClass::addBaseClassData(
             default_fields.push_back(vd);
 
         // get next aligned offset for this type
-        size_t alignsize = vd->type->alignsize();
-        size_t alignedoffset = (offset + alignsize - 1) & ~(alignsize - 1);
+        size_t alignedoffset = realignOffset(offset, vd->type);
 
         // insert explicit padding?
         if (alignedoffset < vd->offset)
diff --git a/ir/irtypestruct.cpp b/ir/irtypestruct.cpp
index 9b08d4fae6..f5d9bf8c06 100644
--- a/ir/irtypestruct.cpp
+++ b/ir/irtypestruct.cpp
@@ -8,6 +8,7 @@
 #include "gen/tollvm.h"
 #include "gen/logger.h"
 #include "gen/utils.h"
+#include "gen/llvmhelpers.h"
 #include "ir/irtypestruct.h"
 
 //////////////////////////////////////////////////////////////////////////////
@@ -192,8 +193,7 @@ const llvm::Type* IrTypeStruct::buildType()
         size_t alignedoffset = offset;
         if (!packed)
         {
-            size_t alignsize = vd->type->alignsize();
-            alignedoffset = (offset + alignsize - 1) & ~(alignsize - 1);
+            alignedoffset = realignOffset(alignedoffset, vd->type);
         }
 
         // insert explicit padding?