diff --git a/objc2-encode/src/encoding.rs b/objc2-encode/src/encoding.rs
index 70746d3d7..4bda9112a 100644
--- a/objc2-encode/src/encoding.rs
+++ b/objc2-encode/src/encoding.rs
@@ -489,11 +489,6 @@ mod tests {
             !"{SomeStruct=}";
         }
 
-        fn struct_unicode() {
-            Encoding::Struct("☃", &[Encoding::Char]);
-            "{☃=c}";
-        }
-
         fn pointer_struct() {
             Encoding::Pointer(&Encoding::Struct("SomeStruct", &[Encoding::Char, Encoding::Int]));
             !Encoding::Pointer(&Encoding::Struct("SomeStruct", &[Encoding::Int, Encoding::Char]));
@@ -590,5 +585,22 @@ mod tests {
             );
             "{abc=^[8B](def=@?)^^b255?}";
         }
+
+        fn identifier() {
+            Encoding::Struct("_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789", &[]);
+            "{_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789=}";
+        }
+    }
+
+    #[test]
+    #[should_panic = "Struct name was not a valid identifier"]
+    fn struct_unicode() {
+        let _ = Encoding::Struct("☃", &[Encoding::Char]).to_string();
+    }
+
+    #[test]
+    #[should_panic = "Union name was not a valid identifier"]
+    fn union_invalid_identifier() {
+        let _ = Encoding::Union("a-b", &[Encoding::Char]).equivalent_to_str("(☃=c)");
     }
 }
diff --git a/objc2-encode/src/helper.rs b/objc2-encode/src/helper.rs
index e67c84c8e..bb64a6b2e 100644
--- a/objc2-encode/src/helper.rs
+++ b/objc2-encode/src/helper.rs
@@ -198,8 +198,32 @@ impl<'a> Helper<'a> {
             Pointer(t) => Self::Indirection(IndirectionKind::Pointer, t),
             Atomic(t) => Self::Indirection(IndirectionKind::Atomic, t),
             Array(len, item) => Self::Array(len, item),
-            Struct(name, fields) => Self::Container(ContainerKind::Struct, name, fields),
-            Union(name, members) => Self::Container(ContainerKind::Union, name, members),
+            Struct(name, fields) => {
+                if !verify_name(name) {
+                    panic!("Struct name was not a valid identifier");
+                }
+                Self::Container(ContainerKind::Struct, name, fields)
+            }
+            Union(name, members) => {
+                if !verify_name(name) {
+                    panic!("Union name was not a valid identifier");
+                }
+                Self::Container(ContainerKind::Union, name, members)
+            }
         }
     }
 }
+
+/// Check whether the name is a valid identifier
+const fn verify_name(name: &str) -> bool {
+    let bytes = name.as_bytes();
+    let mut i = 0;
+    while i < bytes.len() {
+        let byte = bytes[i];
+        if !(byte.is_ascii_alphanumeric() || byte == b'_') {
+            return false;
+        }
+        i += 1;
+    }
+    true
+}