diff --git a/lib/system/jssys.nim b/lib/system/jssys.nim
index 24093a3105..8065f22555 100644
--- a/lib/system/jssys.nim
+++ b/lib/system/jssys.nim
@@ -531,13 +531,13 @@ proc mulInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
 proc divInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   when defined(nimphp):
     asm """
-      return floor(`a` / `b`);
+      return trunc(`a` / `b`);
     """
   else:
     asm """
       if (`b` == 0) `raiseDivByZero`();
       if (`b` == -1 && `a` == 2147483647) `raiseOverflow`();
-      return Math.floor(`a` / `b`);
+      return Math.trunc(`a` / `b`);
     """
 
 proc modInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
@@ -549,7 +549,7 @@ proc modInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
     asm """
       if (`b` == 0) `raiseDivByZero`();
       if (`b` == -1 && `a` == 2147483647) `raiseOverflow`();
-      return Math.floor(`a` % `b`);
+      return Math.trunc(`a` % `b`);
     """
 
 proc addInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
@@ -594,13 +594,13 @@ proc mulInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
 proc divInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
   when defined(nimphp):
     asm """
-      return floor(`a` / `b`);
+      return trunc(`a` / `b`);
     """
   else:
     asm """
       if (`b` == 0) `raiseDivByZero`();
       if (`b` == -1 && `a` == 9223372036854775807) `raiseOverflow`();
-      return Math.floor(`a` / `b`);
+      return Math.trunc(`a` / `b`);
     """
 
 proc modInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
@@ -612,7 +612,7 @@ proc modInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
     asm """
       if (`b` == 0) `raiseDivByZero`();
       if (`b` == -1 && `a` == 9223372036854775807) `raiseOverflow`();
-      return Math.floor(`a` % `b`);
+      return Math.trunc(`a` % `b`);
     """
 
 proc negInt(a: int): int {.compilerproc.} =
diff --git a/tests/js/test2.nim b/tests/js/test2.nim
index 0f460d6f89..0bfb991397 100644
--- a/tests/js/test2.nim
+++ b/tests/js/test2.nim
@@ -2,7 +2,9 @@ discard """
   output: '''foo
 js 3.14
 7
-1'''
+1
+-21550
+-21550'''
 """
 
 # This file tests the JavaScript generator
@@ -40,3 +42,14 @@ procThatRefersToConst() # Call bar before it is defined
 proc procThatRefersToConst() =
   var i = 0 # Use a var index, otherwise nim will constfold foo[0]
   echo someConst[i] # JS exception here: foo is still not initialized (undefined)
+
+# bug #6753
+let x = -1861876800
+const y = 86400
+echo (x - (y - 1)) div y # Now gives `-21550`
+
+proc foo09() =
+    let x = -1861876800
+    const y = 86400
+    echo (x - (y - 1)) div y # Still gives `-21551`
+foo09()