diff --git a/lib/tests/modules.sh b/lib/tests/modules.sh
index 45fd2d624e1e..c6b3fd912a9b 100755
--- a/lib/tests/modules.sh
+++ b/lib/tests/modules.sh
@@ -136,11 +136,11 @@ checkConfigOutput "true" "$@" ./define-module-check.nix
 # Check coerced value.
 checkConfigOutput "\"42\"" config.value ./declare-coerced-value.nix
 checkConfigOutput "\"24\"" config.value ./declare-coerced-value.nix ./define-value-string.nix
-checkConfigError 'The option value .* in .* is not.*string or signed integer.*' config.value ./declare-coerced-value.nix ./define-value-list.nix
+checkConfigError 'The option value .* in .* is not.*string or signed integer convertible to it' config.value ./declare-coerced-value.nix ./define-value-list.nix
 
 # Check coerced value with unsound coercion
 checkConfigOutput "12" config.value ./declare-coerced-value-unsound.nix
-checkConfigError 'The option value .* in .* is not.*8 bit signed integer.* or string.*' config.value ./declare-coerced-value-unsound.nix ./define-value-string-bigint.nix
+checkConfigError 'The option value .* in .* is not.*8 bit signed integer.* or string convertible to it' config.value ./declare-coerced-value-unsound.nix ./define-value-string-bigint.nix
 checkConfigError 'unrecognised JSON value' config.value ./declare-coerced-value-unsound.nix ./define-value-string-arbitrary.nix
 
 cat <<EOF
diff --git a/lib/types.nix b/lib/types.nix
index 45b0ae5042ce..4ee9affcb297 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -256,7 +256,7 @@ rec {
       functor = (defaultFunctor name) // { wrapped = elemType; };
     };
 
-    nonEmptyListOf = elemType: 
+    nonEmptyListOf = elemType:
       let list = addCheck (types.listOf elemType) (l: l != []);
       in list // { description = "non-empty " + list.description; };
 
@@ -419,7 +419,7 @@ rec {
       assert coercedType.getSubModules == null;
       mkOptionType rec {
         name = "coercedTo";
-        description = "${finalType.description} or ${coercedType.description}";
+        description = "${finalType.description} or ${coercedType.description} convertible to it";
         check = x: finalType.check x || (coercedType.check x && finalType.check (coerceFunc x));
         merge = loc: defs:
           let