diff --git a/capi/include/yara_x.h b/capi/include/yara_x.h
index 1dbe05b37..a44fcb56b 100644
--- a/capi/include/yara_x.h
+++ b/capi/include/yara_x.h
@@ -452,9 +452,9 @@ enum YRX_RESULT yrx_compiler_define_global_float(struct YRX_COMPILER *compiler,
 // (e.g., booleans, integers, strings), prefer dedicated functions to avoid
 // the overhead of JSON deserialization.
 //
-// When defining a map, keys must be of string type, and values can be
-// any of the types supported by YARA, including other maps. Arrays must be
-// homogeneous (all elements must be the same type).
+// When defining a map, keys must be of string type and valid YARA identifiers,
+// and values can be any of the types supported by YARA, including other maps.
+// Arrays must be homogeneous (all elements must be the same type).
 enum YRX_RESULT yrx_compiler_define_global_json(struct YRX_COMPILER *compiler,
                                                 const char *ident,
                                                 const char *value);
diff --git a/lib/src/compiler/mod.rs b/lib/src/compiler/mod.rs
index 70e4cda30..f048d0be7 100644
--- a/lib/src/compiler/mod.rs
+++ b/lib/src/compiler/mod.rs
@@ -646,6 +646,12 @@ impl<'a> Compiler<'a> {
     /// `i64`, `i32`, `i16`, `i8`, `u32`, `u16`, `u8`, `f64`, `f32`, `bool`,
     /// `&str`, `String` and [`serde_json::Value`].
     ///
+    /// When using a [`serde_json::Value`] there are certain limitations: keys
+    /// in maps must be valid YARA identifiers (the first character must be `_`
+    /// or a letter, the remaining ones must be `_`, a letter or a digit),
+    /// because these maps are translated into YARA structures. Also, all items
+    /// in an array must have the same type.
+    ///
     /// ```
     /// # use yara_x::Compiler;
     /// assert!(Compiler::new()
diff --git a/lib/src/compiler/tests/mod.rs b/lib/src/compiler/tests/mod.rs
index 191111790..05acf9ce9 100644
--- a/lib/src/compiler/tests/mod.rs
+++ b/lib/src/compiler/tests/mod.rs
@@ -523,10 +523,17 @@ fn globals_json() {
 
     assert_eq!(
         Compiler::new()
-            .define_global("invalid_array", json!({ "foo": null }))
+            .define_global("invalid_struct", json!({ "foo": null }))
             .unwrap_err(),
         VariableError::UnexpectedNull
     );
+
+    assert_eq!(
+        Compiler::new()
+            .define_global("invalid_struct", json!({ "/foo": 1 }))
+            .unwrap_err(),
+        VariableError::InvalidIdentifier("/foo".to_string())
+    );
 }
 
 #[test]
diff --git a/lib/src/variables.rs b/lib/src/variables.rs
index 62c60d084..9b7a7d3c2 100644
--- a/lib/src/variables.rs
+++ b/lib/src/variables.rs
@@ -37,7 +37,7 @@ pub enum VariableError {
 
     /// The identifier is not valid. Identifiers can only contain alphanumeric
     /// characters and underscores, and can't start with a digit.
-    #[error("invalid variable identifier `{0}`")]
+    #[error("invalid identifier `{0}`")]
     InvalidIdentifier(String),
 
     /// The value of a variable cannot be null. This may happen when using a
@@ -303,6 +303,11 @@ impl TryFrom<&serde_json::Value> for Variable {
             serde_json::Value::Object(obj) => {
                 let mut s = types::Struct::new();
                 for (key, value) in obj {
+                    if !is_valid_identifier(key) {
+                        return Err(VariableError::InvalidIdentifier(
+                            key.to_string(),
+                        ));
+                    }
                     s.add_field(
                         key,
                         TypeValue::from(Variable::try_from(value)?),
diff --git a/py/src/lib.rs b/py/src/lib.rs
index 03916a3ed..a305bd333 100644
--- a/py/src/lib.rs
+++ b/py/src/lib.rs
@@ -497,7 +497,10 @@ impl Compiler {
     /// each scanner can change the variable's value by calling
     /// [`crate::Scanner::set_global`].
     ///
-    /// The type of `value` must be: bool, str, bytes, int or float.
+    /// The type of `value` must be: bool, str, bytes, int, float or dict. When
+    /// the value is a dict, keys must be of type string and valid YARA identifiers
+    /// (the first character must be `_` or a letter, and the remaining ones must
+    /// be a `_`, a letter or a digit).
     ///
     /// # Raises
     ///
diff --git a/py/yara_x.pyi b/py/yara_x.pyi
index 358c7652e..5067688c4 100644
--- a/py/yara_x.pyi
+++ b/py/yara_x.pyi
@@ -96,7 +96,10 @@ class Compiler:
         each scanner can change the variable's value by calling
         [`crate::Scanner::set_global`].
 
-        The type of `value` must be: bool, str, bytes, int or float.
+        The type of `value` must be: bool, str, bytes, int, float or dict. When
+        the value is a dict, keys must be of type string and valid YARA identifiers
+        (the first character must be `_` or a letter, and the remaining ones must
+        be a `_`, a letter or a digit).
 
         # Raises