diff --git a/layout/generic/nsGridContainerFrame.cpp b/layout/generic/nsGridContainerFrame.cpp
index f2cc3f1a6afb..8fa1c93f1b19 100644
--- a/layout/generic/nsGridContainerFrame.cpp
+++ b/layout/generic/nsGridContainerFrame.cpp
@@ -449,7 +449,9 @@ TrackSize::StateBits nsGridContainerFrame::TrackSize::Initialize(
   if (aSize.IsFitContent()) {
     // In layout, fit-content(size) behaves as minmax(auto, max-content), with
     // 'size' as an additional upper-bound.
-    mState = eFitContent;
+    if (!::IsPercentOfIndefiniteSize(aSize.AsFitContent(), aPercentageBasis)) {
+      mState = eFitContent;
+    }
     minSizeTag = Tag::Auto;
     maxSizeTag = Tag::MaxContent;
   }
diff --git a/testing/web-platform/tests/css/css-grid/layout-algorithm/grid-fit-content-percentage.html b/testing/web-platform/tests/css/css-grid/layout-algorithm/grid-fit-content-percentage.html
index 892dbe40b468..22683fef14f0 100644
--- a/testing/web-platform/tests/css/css-grid/layout-algorithm/grid-fit-content-percentage.html
+++ b/testing/web-platform/tests/css/css-grid/layout-algorithm/grid-fit-content-percentage.html
@@ -36,30 +36,34 @@ function clamp(value, min, max) {
 }
 const minContent = 50;
 const maxContent = 100;
-for (const use_calc of [false, true]) {
-  for (const percentage of [0, 50, 75, 100, 150]) {
-    const value = use_calc ? `fit-content(calc(0px + ${percentage}%))`
-                           : `fit-content(${percentage}%)`;
-    const container = document.createElement("div");
-    container.className = "container";
-    document.body.appendChild(container);
-    const grid = document.createElement("div");
-    grid.className = "grid";
-    grid.style.gridTemplateColumns = value;
-    container.appendChild(grid);
-    const item = document.createElement("div");
-    item.className = "item";
-    grid.appendChild(item);
-    test(function() {
-      const colSize = clamp(percentage * maxContent / 100, minContent, maxContent);
-      const height = colSize < maxContent ? maxContent : minContent;
-      assert_equals(item.offsetWidth, colSize, "Grid item width");
-      assert_equals(item.offsetHeight, height, "Grid item height");
-      assert_equals(grid.offsetWidth, maxContent, "Grid container width");
-      assert_equals(grid.offsetHeight, height, "Grid container height");
-      assert_equals(getComputedStyle(grid).gridTemplateColumns, colSize + "px",
-                    "Grid column size");
-    }, value);
+for (const use_min_width of [false, true]) {
+  for (const use_calc of [false, true]) {
+    for (const percentage of [0, 50, 75, 100, 150]) {
+      const value = use_calc ? `fit-content(calc(0px + ${percentage}%))`
+                            : `fit-content(${percentage}%)`;
+      const container = document.createElement("div");
+      container.className = "container";
+      document.body.appendChild(container);
+      const grid = document.createElement("div");
+      grid.className = "grid";
+      grid.style.gridTemplateColumns = value;
+      container.appendChild(grid);
+      const item = document.createElement("div");
+      item.className = "item";
+      item.style.minWidth = use_min_width ? "auto" : "0px";
+      grid.appendChild(item);
+      test(function() {
+        const minWidth = use_min_width ? minContent : 0;
+        const colSize = clamp(percentage * maxContent / 100, minWidth, maxContent);
+        const height = colSize < maxContent ? maxContent : minContent;
+        assert_equals(item.offsetWidth, colSize, "Grid item width");
+        assert_equals(item.offsetHeight, height, "Grid item height");
+        assert_equals(grid.offsetWidth, maxContent, "Grid container width");
+        assert_equals(grid.offsetHeight, height, "Grid container height");
+        assert_equals(getComputedStyle(grid).gridTemplateColumns, colSize + "px",
+                      "Grid column size");
+      }, value + "; min-width: " + item.style.minWidth);
+    }
   }
 }
 </script>