diff --git a/src/builtins/printf.cpp b/src/builtins/printf.cpp
index dc8c2dfc9..d5b8e81aa 100644
--- a/src/builtins/printf.cpp
+++ b/src/builtins/printf.cpp
@@ -262,7 +262,7 @@ void builtin_printf_state_t::verify_numeric(const wchar_t *s, const wchar_t *end
             this->fatal_error(_(L"%ls: expected a numeric value"), s);
         } else {
             // This isn't entirely fatal - the value should still be printed.
-            this->nonfatal_error(_(L"%ls: value not completely converted"), s);
+            this->nonfatal_error(_(L"%ls: value not completely converted (can't convert '%ls')"), s, end);
         }
     }
 }
diff --git a/tests/checks/printf.fish b/tests/checks/printf.fish
index 83da2c878..5c6f13405 100644
--- a/tests/checks/printf.fish
+++ b/tests/checks/printf.fish
@@ -66,7 +66,7 @@ printf '%e\n' "1.23" # should succeed, output should be 1.230000e+00
 
 printf '%e\n' "2,34" # should fail
 # CHECK: 2.000000e+00
-# CHECKERR: 2,34: value not completely converted
+# CHECKERR: 2,34: value not completely converted (can't convert ',34')
 
 # Verify long long ints are handled correctly. See issue #3352.
 printf 'long hex1 %x\n' 498216206234
@@ -92,6 +92,6 @@ echo $status
 # Verify numeric conversion still happens even if it couldn't be fully converted
 printf '%d\n' 15.1
 # CHECK: 15
-# CHECKERR: 15.1: value not completely converted
+# CHECKERR: 15.1: value not completely converted (can't convert '.1')
 echo $status
 # CHECK: 1