diff --git a/.chronus/changes/fix-NRE-generate-model-2026-0-19-9-51-29.md b/.chronus/changes/fix-NRE-generate-model-2026-0-19-9-51-29.md
new file mode 100644
index 00000000000..6def08dc384
--- /dev/null
+++ b/.chronus/changes/fix-NRE-generate-model-2026-0-19-9-51-29.md
@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/openapi3"
+---
+
+importer - null reference exception if member schema cannot be resolved
\ No newline at end of file
diff --git a/packages/openapi3/src/cli/actions/convert/generators/generate-model.ts b/packages/openapi3/src/cli/actions/convert/generators/generate-model.ts
index c30f4c11f40..f73040d194b 100644
--- a/packages/openapi3/src/cli/actions/convert/generators/generate-model.ts
+++ b/packages/openapi3/src/cli/actions/convert/generators/generate-model.ts
@@ -245,10 +245,12 @@ function generateUnion(union: TypeSpecUnion, context: Context): string {
       return "";
     }
 
-    const memberSchema = "$ref" in member ? context.getSchemaByRef(member.$ref)! : member;
+    const memberSchema = "$ref" in member ? context.getSchemaByRef(member.$ref) : member;
 
     const propertySchema =
-      memberSchema.properties && memberSchema.properties[union.schema.discriminator.propertyName];
+      memberSchema &&
+      memberSchema.properties &&
+      memberSchema.properties[union.schema.discriminator.propertyName];
     const value =
       (union.schema.discriminator?.mapping && "$ref" in member
         ? Object.entries(union.schema.discriminator.mapping).find((x) => x[1] === member.$ref)?.[0]