diff --git a/src/ddmd/dclass.d b/src/ddmd/dclass.d
index b89f85e15b97..e1023c7d041d 100644
--- a/src/ddmd/dclass.d
+++ b/src/ddmd/dclass.d
@@ -967,6 +967,18 @@ extern (C++) class ClassDeclaration : AggregateDeclaration
 
         sc2.pop();
 
+        if (type.ty == Tclass && (cast(TypeClass)type).sym != this)
+        {
+            // https://issues.dlang.org/show_bug.cgi?id=17492
+            ClassDeclaration cd = (cast(TypeClass)type).sym;
+            version (none)
+            {
+                printf("this = %p %s\n", this, this.toPrettyChars());
+                printf("type = %d sym = %p, %s\n", type.ty, cd, cd.toPrettyChars());
+            }
+            error("already exists at %s. Perhaps in another function with the same name?", cd.loc.toChars());
+        }
+
         if (global.errors != errors)
         {
             // The type is no good.
@@ -995,16 +1007,6 @@ extern (C++) class ClassDeclaration : AggregateDeclaration
             deferred.semantic2(sc);
             deferred.semantic3(sc);
         }
-
-        version (none)
-        {
-            if (type.ty == Tclass && (cast(TypeClass)type).sym != this)
-            {
-                printf("this = %p %s\n", this, this.toChars());
-                printf("type = %d sym = %p\n", type.ty, (cast(TypeClass)type).sym);
-            }
-        }
-        assert(type.ty != Tclass || (cast(TypeClass)type).sym == this);
         //printf("-ClassDeclaration.semantic(%s), type = %p, sizeok = %d, this = %p\n", toChars(), type, sizeok, this);
     }
 
diff --git a/test/fail_compilation/fail17492.d b/test/fail_compilation/fail17492.d
new file mode 100644
index 000000000000..e45c2e59359e
--- /dev/null
+++ b/test/fail_compilation/fail17492.d
@@ -0,0 +1,23 @@
+/* TEST_OUTPUT:
+---
+fail_compilation/fail17492.d(19): Error: class fail17492.C.testE.I already exists at fail_compilation/fail17492.d(12). Perhaps in another function with the same name?
+---
+https://issues.dlang.org/show_bug.cgi?id=17492
+*/
+
+class C
+{
+    void testE()
+    {
+        class I
+        {
+        }
+    }
+
+    void testE()
+    {
+        class I
+        {
+        }
+    }
+}