diff --git a/src/test-generation.adb b/src/test-generation.adb
index e63b5a68..84582bbe 100644
--- a/src/test-generation.adb
+++ b/src/test-generation.adb
@@ -69,6 +69,15 @@ package body Test.Generation is
          return Over;
       end if;
 
+      --  Skip any non-instantiated generic decl, they will be processed as
+      --  part of a generic instantiation, if any.
+
+      if Node.Kind in Ada_Generic_Decl
+        and then Node.P_Generic_Instantiations'Length = 0
+      then
+         return Over;
+      end if;
+
       --  Collect all types used as parameters in subprogram declarations.
       --  Skip generic subprogram declarations as we only care about the
       --  instantiations. Also skip subprograms with zero parameters if there
@@ -86,14 +95,6 @@ package body Test.Generation is
         | Ada_Subp_Renaming_Decl
       then
 
-         --  Skip generic subp decls (these will be processed if they are
-         --  instantiated).
-
-         if Node.As_Basic_Decl.P_Canonical_Part.Kind in Ada_Generic_Decl
-         then
-            return Over;
-         end if;
-
          --  Check, if the subprogram has zero parameters. If so, only add it
          --  to the generation context if it has a global annotation.
 
diff --git a/testsuite/tests/test/183-formal_params/gen.adb b/testsuite/tests/test/183-formal_params/gen.adb
new file mode 100644
index 00000000..cf79cc65
--- /dev/null
+++ b/testsuite/tests/test/183-formal_params/gen.adb
@@ -0,0 +1,10 @@
+package body Gen is
+
+   procedure Params (X : T) is
+   begin
+      null;
+   end Params;
+
+   function Ret return T is (Val);
+
+end Gen;
diff --git a/testsuite/tests/test/183-formal_params/gen.ads b/testsuite/tests/test/183-formal_params/gen.ads
new file mode 100644
index 00000000..02a50d1a
--- /dev/null
+++ b/testsuite/tests/test/183-formal_params/gen.ads
@@ -0,0 +1,7 @@
+generic
+   type T is range <>;
+   Val : T;
+package Gen is
+   procedure Params (X : T);
+   function Ret return T;
+end Gen;
\ No newline at end of file
diff --git a/testsuite/tests/test/183-formal_params/importing.ads b/testsuite/tests/test/183-formal_params/importing.ads
new file mode 100644
index 00000000..4c397ed9
--- /dev/null
+++ b/testsuite/tests/test/183-formal_params/importing.ads
@@ -0,0 +1,5 @@
+with Gen;
+
+package Importing is
+
+end Importing;
diff --git a/testsuite/tests/test/183-formal_params/prj.gpr b/testsuite/tests/test/183-formal_params/prj.gpr
new file mode 100644
index 00000000..1c32e054
--- /dev/null
+++ b/testsuite/tests/test/183-formal_params/prj.gpr
@@ -0,0 +1,5 @@
+project Prj is
+
+   for Object_Dir use "obj";
+
+end Prj;
diff --git a/testsuite/tests/test/183-formal_params/test.out b/testsuite/tests/test/183-formal_params/test.out
new file mode 100644
index 00000000..5461b50b
--- /dev/null
+++ b/testsuite/tests/test/183-formal_params/test.out
@@ -0,0 +1,7 @@
+No subprogram supported for test case generation.
+Units remaining: 3     
Units remaining: 2     
Units remaining: 1     
warning: (gnattest) gen.ads:1:1: no instance of Gen
+ corresponding tests are not included into harness
+gnattest: no test skeletons generated because no subprogram to test
+          found in project /prj.gpr
+gnattest: cannot create main suite and test runner
+>>>program returned status code 1
diff --git a/testsuite/tests/test/183-formal_params/test.sh b/testsuite/tests/test/183-formal_params/test.sh
new file mode 100644
index 00000000..4b5a8786
--- /dev/null
+++ b/testsuite/tests/test/183-formal_params/test.sh
@@ -0,0 +1,5 @@
+#! /bin/bash
+
+# We expect only diagnostics stating that there are no
+# subprograms to test, not that some type is unsupported.
+gnattest -P prj.gpr --gen-test-vectors
diff --git a/testsuite/tests/test/183-formal_params/test.yaml b/testsuite/tests/test/183-formal_params/test.yaml
new file mode 100644
index 00000000..6665c4a3
--- /dev/null
+++ b/testsuite/tests/test/183-formal_params/test.yaml
@@ -0,0 +1,7 @@
+description: Test that gnattest does not attempt to generate test inputs for
+  subprograms with generic formal parameters or return types.
+
+driver: shell_script
+
+control:
+    - [XFAIL, 'x86', 'Marshalling not working for 32bits (UB03-008)']
diff --git a/testsuite/tests/test/tc_json_dump_with_gen/test.out b/testsuite/tests/test/tc_json_dump_with_gen/test.out
index 422ef15c..526d695a 100644
--- a/testsuite/tests/test/tc_json_dump_with_gen/test.out
+++ b/testsuite/tests/test/tc_json_dump_with_gen/test.out
@@ -1,3 +1,6 @@
+gnattest: Error while processing <ExprFunction ["Ident"] my_file.ads:78:4-78:43>:
+my_file.ident.X: my_file.ident.t is not supported (Generic formal types are unsupported)
+
 Units remaining: 2     
Units remaining: 1     
 my_file.ads:14:4: info: corresponding test PASSED
 my_file.ads:14:4: info: corresponding test PASSED