diff --git a/gen/cheader.tmpl b/gen/cheader.tmpl
index 84597714..d491c67e 100644
--- a/gen/cheader.tmpl
+++ b/gen/cheader.tmpl
@@ -312,7 +312,7 @@ typedef struct WGPU{{.Name | PascalCase}}CallbackInfo{{$.ExtSuffix}} {
 /**
  * Initializer for @ref WGPU{{.Name | PascalCase}}CallbackInfo{{$.ExtSuffix}}.
  */
-#define WGPU_{{.Name | ConstantCase}}_CALLBACK_INFO{{$.ExtSuffix}}_INIT _wgpu_MAKE_INIT_STRUCT(WGPU{{.Name | PascalCase}}CallbackInfo{{$.ExtSuffix}}, { \
+#define WGPU_{{.Name | ConstantCase}}_CALLBACK_INFO{{if $.ExtSuffix}}_{{$.ExtSuffix}}{{end}}_INIT _wgpu_MAKE_INIT_STRUCT(WGPU{{.Name | PascalCase}}CallbackInfo{{$.ExtSuffix}}, { \
     /*.nextInChain=*/NULL _wgpu_COMMA \
 {{-   if eq .Style "callback_mode" }}
     /*.mode=*/WGPUCallbackMode_WaitAnyOnly _wgpu_COMMA \
diff --git a/gen/gen.go b/gen/gen.go
index e82b3159..277221a7 100644
--- a/gen/gen.go
+++ b/gen/gen.go
@@ -590,11 +590,11 @@ func (g *Generator) DefaultValue(member ParameterType, isDocString bool) string
 			return literal("NULL")
 		} else {
 			typ := strings.TrimPrefix(member.Type, "struct.")
-			return ref("WGPU_" + ConstantCase(typ) + "_INIT")
+			return ref("WGPU_" + ConstantCase(typ) + g.ConstantExtSuffix() + "_INIT")
 		}
 	case strings.HasPrefix(member.Type, "callback."):
 		typ := strings.TrimPrefix(member.Type, "callback.")
-		return ref("WGPU_" + ConstantCase(typ) + "_CALLBACK_INFO_INIT")
+		return ref("WGPU_" + ConstantCase(typ) + "_CALLBACK_INFO" + g.ConstantExtSuffix() + "_INIT")
 	case strings.HasPrefix(member.Type, "object."):
 		return literal("NULL")
 	case strings.HasPrefix(member.Type, "array<"):
@@ -607,3 +607,11 @@ func (g *Generator) DefaultValue(member ParameterType, isDocString bool) string
 		panic("invalid prefix: " + member.Type + " in member " + member.Name)
 	}
 }
+
+func (g *Generator) ConstantExtSuffix() string {
+	if g.ExtSuffix != "" {
+		return "_" + ConstantCase(g.ExtSuffix)
+	} else {
+		return ""
+	}
+}