diff --git a/src/dobjtype.cpp b/src/dobjtype.cpp
index 609ec1721..121c0fb27 100644
--- a/src/dobjtype.cpp
+++ b/src/dobjtype.cpp
@@ -2403,22 +2403,23 @@ PClass *PClass::CreateDerivedClass(FName name, unsigned int size)
 
 //==========================================================================
 //
-// PClass:: Extend
+// PClass :: Extend
 //
-// Add <extension> bytes to the end of this class. Returns the previous
-// size of the class.
+// Add <extension> bytes to the end of this class and possibly more to meet
+// alignment restrictions. Returns the start of the extended block.
 //
 //==========================================================================
 
-unsigned int PClass::Extend(unsigned int extension)
+unsigned int PClass::Extend(unsigned int extension, unsigned int alignment)
 {
 	assert(this->bRuntimeClass);
 
 	unsigned int oldsize = Size;
-	Size += extension;
+	unsigned int padto = (oldsize + alignment - 1) & ~(alignment - 1);
+	Size = padto + extension;
 	Defaults = (BYTE *)M_Realloc(Defaults, Size);
-	memset(Defaults + oldsize, 0, extension);
-	return oldsize;
+	memset(Defaults + oldsize, 0, Size - oldsize);
+	return padto;
 }
 
 //==========================================================================
diff --git a/src/dobjtype.h b/src/dobjtype.h
index b482efe45..05097795b 100644
--- a/src/dobjtype.h
+++ b/src/dobjtype.h
@@ -660,7 +660,8 @@ public:
 	void InsertIntoHash();
 	DObject *CreateNew() const;
 	PClass *CreateDerivedClass(FName name, unsigned int size);
-	unsigned int Extend(unsigned int extension);
+	unsigned int Extend(unsigned int extension, unsigned int alignment);
+	unsigned int Extend(const PType *type) { return Extend(type->Size, type->Align); }
 	void InitializeActorInfo();
 	void BuildFlatPointers();
 	const PClass *NativeClass() const;
diff --git a/src/thingdef/thingdef_parse.cpp b/src/thingdef/thingdef_parse.cpp
index 97e22dc8c..cc2c71e34 100644
--- a/src/thingdef/thingdef_parse.cpp
+++ b/src/thingdef/thingdef_parse.cpp
@@ -531,14 +531,14 @@ static void ParseUserVariable (FScanner &sc, PSymbolTable *symt, PClassActor *cl
 		sc.ScriptError("Native classes may not have user variables");
 	}
 
-	// Read the type and make sure it's int.
+	// Read the type and make sure it's acceptable.
 	sc.MustGetAnyToken();
-	if (sc.TokenType != TK_Int)
+	if (sc.TokenType != TK_Int && sc.TokenType != TK_Float)
 	{
-		sc.ScriptMessage("User variables must be of type int");
+		sc.ScriptMessage("User variables must be of type 'int' or 'float'");
 		FScriptPosition::ErrorCounter++;
 	}
-	type = TypeSInt32;
+	type = sc.TokenType == TK_Int ? (PType *)TypeSInt32 : (PType *)TypeFloat64;
 
 	sc.MustGetToken(TK_Identifier);
 	// For now, restrict user variables to those that begin with "user_" to guarantee
@@ -585,7 +585,7 @@ static void ParseUserVariable (FScanner &sc, PSymbolTable *symt, PClassActor *cl
 	sc.MustGetToken(';');
 
 	PField *sym = new PField(symname, type, 0);
-	sym->Offset = cls->Extend(sizeof(int) * maxelems);
+	sym->Offset = cls->Extend(type);
 	if (symt->AddSymbol(sym) == NULL)
 	{
 		delete sym;