diff --git a/src/internal/runtime/maps/table.go b/src/internal/runtime/maps/table.go
index d4b9276b57078f..480d12df2e2f73 100644
--- a/src/internal/runtime/maps/table.go
+++ b/src/internal/runtime/maps/table.go
@@ -8,6 +8,7 @@ package maps
 import (
 	"internal/abi"
 	"internal/goarch"
+	"internal/runtime/math"
 	"unsafe"
 )
 
@@ -127,8 +128,7 @@ func (t *table) maxGrowthLeft() uint16 {
 		// single-group tables, we could fill all slots.
 		return t.capacity - 1
 	} else {
-		if t.capacity*maxAvgGroupLoad < t.capacity {
-			// TODO(prattmic): Do something cleaner.
+		if t.capacity > math.MaxUint16/maxAvgGroupLoad {
 			panic("overflow")
 		}
 		return (t.capacity * maxAvgGroupLoad) / abi.MapGroupSlots
diff --git a/src/internal/runtime/math/math.go b/src/internal/runtime/math/math.go
index 7b616cff797740..0af5aa3f7610d8 100644
--- a/src/internal/runtime/math/math.go
+++ b/src/internal/runtime/math/math.go
@@ -7,6 +7,7 @@ package math
 import "internal/goarch"
 
 const (
+	MaxUint16  = ^uint16(0)
 	MaxUint32  = ^uint32(0)
 	MaxUint64  = ^uint64(0)
 	MaxUintptr = ^uintptr(0)