diff --git a/dom/canvas/CanvasRenderingContext2D.cpp b/dom/canvas/CanvasRenderingContext2D.cpp
index a7d937fd3c..60078a8fcb 100644
--- a/dom/canvas/CanvasRenderingContext2D.cpp
+++ b/dom/canvas/CanvasRenderingContext2D.cpp
@@ -2094,7 +2094,10 @@ CanvasRenderingContext2D::GetInputStream(const char* aMimeType,
 
   bool PoisonData = Preferences::GetBool("canvas.poisondata",false);
   if (PoisonData) {
-    srand(time(NULL));
+    int PoisonInterval = Preferences::GetInt("canvas.poisondata.interval", 300);
+    PoisonInterval = (PoisonInterval < 1) ? 1 : (PoisonInterval > 28800) ? 28800 : PoisonInterval;
+    unsigned int epoch = time(nullptr);
+    srand(epoch / PoisonInterval);
     // Image buffer is always a packed BGRA array (BGRX -> BGR[FF])
     // so always 4-byte pixels.
     // GetImageBuffer => SurfaceToPackedBGRA [=> ConvertBGRXToBGRA]
@@ -5775,9 +5778,13 @@ CanvasRenderingContext2D::GetImageDataArray(JSContext* aCx,
 
   MOZ_ASSERT(aWidth && aHeight);
 
-  bool PoisonData = Preferences::GetBool("canvas.poisondata",false);
-  if (PoisonData)
-    srand(time(NULL));
+  bool PoisonData = Preferences::GetBool("canvas.poisondata", false);
+  if (PoisonData) {
+    int PoisonInterval = Preferences::GetInt("canvas.poisondata.interval", 300);
+    PoisonInterval = (PoisonInterval < 1) ? 1 : (PoisonInterval > 28800) ? 28800 : PoisonInterval;
+    unsigned int epoch = time(nullptr);
+    srand(epoch / PoisonInterval);
+  }
 
   CheckedInt<uint32_t> len = CheckedInt<uint32_t>(aWidth) * aHeight * 4;
   if (!len.isValid()) {
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 682000aaf2..56c82aa1d9 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -4305,6 +4305,9 @@ pref("canvas.image.cache.limit", 0);
 // Allow track-fobics to deliberately poison canvas data for
 // toDataURL() and getImageData()
 pref("canvas.poisondata", false);
+// Rotate randomness of data poisoning every n seconds. Default 5 minutes.
+// Valid range [1..28800] (1s-8h).
+pref("canvas.poisondata.interval", 300);
 
 // WebGL prefs
 pref("gl.msaa-level", 2);