diff --git a/src/compiler/translator/Types.cpp b/src/compiler/translator/Types.cpp
index c0882da9b1..77d4ff9b8b 100644
--- a/src/compiler/translator/Types.cpp
+++ b/src/compiler/translator/Types.cpp
@@ -472,12 +472,21 @@ const char *TType::buildMangledName() const
                 {
                     mangledName += mStructure->name().data();
                 }
+                // Separator between the user-chosen struct name and the mangled
+                // field list. The field-list mangling alphabet ([0-9A-F][01][A-Za-z])
+                // is a subset of the GLSL identifier alphabet, so without a
+                // separator two structurally distinct structs can produce the
+                // same mangled name (e.g. struct A00B{vec4 y;} vs
+                // struct A{float x;vec4 y;}). ';' is not a valid GLSL identifier
+                // character and is not produced by any other mangling routine.
+                mangledName += ';';
                 mangledName += mStructure->mangledFieldList();
                 mangledName += '}';
                 break;
             case EbtInterfaceBlock:
                 mangledName += "{i";
                 mangledName += mInterfaceBlock->name().data();
+                mangledName += ';';
                 mangledName += mInterfaceBlock->mangledFieldList();
                 mangledName += '}';
                 break;