diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index f3640e6299..a11035a931 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -2784,7 +2784,8 @@ static int eval7_leader(typval_T *const rettv, const bool numeric_only,
           break;
         }
         if (rettv->v_type == VAR_FLOAT) {
-          f = !(bool)f;
+          rettv->v_type = VAR_BOOL;
+          val = f == 0.0 ? kBoolVarTrue : kBoolVarFalse;
         } else {
           val = !val;
         }
diff --git a/test/old/testdir/test_vimscript.vim b/test/old/testdir/test_vimscript.vim
index e0f805baea..458eae9134 100644
--- a/test/old/testdir/test_vimscript.vim
+++ b/test/old/testdir/test_vimscript.vim
@@ -7017,10 +7017,14 @@ func Test_compound_assignment_operators()
       call assert_equal(10.5, x)
       let x /= 2.5
       call assert_equal(4.2, x)
-      call assert_fails('let x %= 0.5', 'E734')
-      call assert_fails('let x .= "f"', 'E734')
+      call assert_fails('let x %= 0.5', 'E734:')
+      call assert_fails('let x .= "f"', 'E734:')
       let x = !3.14
-      call assert_equal(0.0, x)
+      call assert_equal(0, x)
+      call assert_equal(1, !!1.0)
+      let x = !0.0
+      call assert_equal(1, x)
+      call assert_equal(0, !!0.0)
 
       " integer and float operations
       let x = 1