diff --git a/lib/decimal/decimal_test.go b/lib/decimal/decimal_test.go
index 4e2e271ef..4bc74130e 100644
--- a/lib/decimal/decimal_test.go
+++ b/lib/decimal/decimal_test.go
@@ -506,8 +506,9 @@ func TestFloatToDecimalRoundtrip(t *testing.T) {
 	f(vMin)
 	f(vStaleNaN)
 
+	r := rand.New(rand.NewSource(1))
 	for i := 0; i < 1e4; i++ {
-		v := rand.NormFloat64()
+		v := r.NormFloat64()
 		f(v)
 		f(v * 1e-6)
 		f(v * 1e6)
diff --git a/lib/decimal/decimal_timing_test.go b/lib/decimal/decimal_timing_test.go
index ceba29d2f..b7d451bb4 100644
--- a/lib/decimal/decimal_timing_test.go
+++ b/lib/decimal/decimal_timing_test.go
@@ -84,17 +84,19 @@ func benchmarkAppendFloatToDecimal(b *testing.B, fa []float64) {
 }
 
 var testFAReal = func() []float64 {
+	r := rand.New(rand.NewSource(1))
 	fa := make([]float64, 8*1024)
 	for i := 0; i < len(fa); i++ {
-		fa[i] = rand.NormFloat64() * 1e-6
+		fa[i] = r.NormFloat64() * 1e-6
 	}
 	return fa
 }()
 
 var testFAInteger = func() []float64 {
+	r := rand.New(rand.NewSource(2))
 	fa := make([]float64, 8*1024)
 	for i := 0; i < len(fa); i++ {
-		fa[i] = float64(int(rand.NormFloat64() * 1e6))
+		fa[i] = float64(int(r.NormFloat64() * 1e6))
 	}
 	return fa
 }()