diff --git a/jsonapi.go b/jsonapi.go
index ec66454c6..37a14c121 100644
--- a/jsonapi.go
+++ b/jsonapi.go
@@ -781,11 +781,11 @@ func JSONToAmount(jsonAmount float64) (int64, error) {
 	var amount int64
 	var err error
 	if jsonAmount > 1.797693134862315708145274237317043567981e+300 {
-		err := fmt.Errorf("Error %d is too large to convert", jsonAmount)
+		err := fmt.Errorf("Error %v is too large to convert", jsonAmount)
 		return amount, err
 	}
 	if jsonAmount < -1.797693134862315708145274237317043567981e+300 {
-		err := fmt.Errorf("Error %d is too small to convert", jsonAmount)
+		err := fmt.Errorf("Error %v is too small to convert", jsonAmount)
 		return amount, err
 	}
 	tempVal := 1e8 * jsonAmount
diff --git a/jsonapi_test.go b/jsonapi_test.go
index 74f7bc7b1..db8aa9ed6 100644
--- a/jsonapi_test.go
+++ b/jsonapi_test.go
@@ -287,11 +287,11 @@ func TestJSONtoAmount(t *testing.T) {
 		res, err := btcjson.JSONToAmount(tt.in)
 		if tt.pass {
 			if res != tt.out || err != nil {
-				t.Errorf("Should not fail: ", tt.in)
+				t.Errorf("Should not fail: %v", tt.in)
 			}
 		} else {
 			if err == nil {
-				t.Errorf("Should not pass: ", tt.in)
+				t.Errorf("Should not pass: %v", tt.in)
 			}
 		}
 	}