diff --git a/eqwalizer/test_projects/_cli/otp_funs.cli b/eqwalizer/test_projects/_cli/otp_funs.cli
index 0384989..37a44a0 100644
--- a/eqwalizer/test_projects/_cli/otp_funs.cli
+++ b/eqwalizer/test_projects/_cli/otp_funs.cli
@@ -14,10 +14,10 @@ ets  16
 filename  21
 gb_sets  26
 proplists  51
-maps  149
+maps  150
 lists  169
 erlang  396
 Per app stats:
 kernel  21
 erts  396
-stdlib  471
+stdlib  472
diff --git a/eqwalizer/test_projects/check/src/custom.erl b/eqwalizer/test_projects/check/src/custom.erl
index 1d7b31b..35845e3 100644
--- a/eqwalizer/test_projects/check/src/custom.erl
+++ b/eqwalizer/test_projects/check/src/custom.erl
@@ -2284,3 +2284,14 @@ re_replace_5_neg(Subj) ->
 re_replace_6_neg(Subj) ->
     Res = re:replace(Subj, "+", "-", [{return, something}]),
     Res.
+
+-spec maps_fold_keys(#{a => atom(), b => atom()}) -> ok.
+maps_fold_keys(M) ->
+    maps:fold(
+        fun(K, _V, Acc) -> process_key(K), Acc end,
+        ok,
+        M
+    ).
+
+-spec process_key(a | b) -> ok.
+process_key(_K) -> ok.
\ No newline at end of file
diff --git a/eqwalizer/test_projects/check/src/custom.erl.check b/eqwalizer/test_projects/check/src/custom.erl.check
index 8fba682..9eabde9 100644
--- a/eqwalizer/test_projects/check/src/custom.erl.check
+++ b/eqwalizer/test_projects/check/src/custom.erl.check
@@ -3081,3 +3081,20 @@ re_replace_6_neg(Subj) ->                  | ERROR   |
                                            |         |   because
                                            |         |   'something' is not compatible with 'iodata' | 'list' | 'binary'
     Res.                                   |         |
+                                           |         |
+-spec maps_fold_keys(#{a => atom(), b => a……         |
+maps_fold_keys(M) ->                       | ERROR   |
+    maps:fold(                             |         |
+        fun(K, _V, Acc) -> process_key(K),……         | K.
+                                           |         | Expression has type:   atom()
+                                           |         | Context expected type: 'a' | 'b'
+                                           |         | 
+                                           |         |   atom() is not compatible with 'a' | 'b'
+                                           |         |   because
+                                           |         |   atom() is not compatible with 'a'
+        ok,                                |         |
+        M                                  |         |
+    ).                                     |         |
+                                           |         |
+-spec process_key(a | b) -> ok.            |         |
+process_key(_K) -> ok.                     | OK      |