diff --git a/components/layout/block.rs b/components/layout/block.rs
index e61ad3104c8..b01a31804b2 100644
--- a/components/layout/block.rs
+++ b/components/layout/block.rs
@@ -1465,8 +1465,8 @@ impl Flow for BlockFlow {
 
         // Find the maximum inline-size from children.
         let mut computation = self.fragment.compute_intrinsic_inline_sizes();
-        let mut left_float_width = Au(0);
-        let mut right_float_width = Au(0);
+        let (mut left_float_width, mut right_float_width) = (Au(0), Au(0));
+        let (mut left_float_width_accumulator, mut right_float_width_accumulator) = (Au(0), Au(0));
         for kid in self.base.child_iter() {
             let is_absolutely_positioned =
                 flow::base(kid).flags.contains(IS_ABSOLUTELY_POSITIONED);
@@ -1477,6 +1477,15 @@ impl Flow for BlockFlow {
                     max(computation.content_intrinsic_sizes.minimum_inline_size,
                         child_base.intrinsic_inline_sizes.minimum_inline_size);
 
+                if child_base.flags.contains(CLEARS_LEFT) {
+                    left_float_width = Au::max(left_float_width, left_float_width_accumulator);
+                    left_float_width_accumulator = Au(0)
+                }
+                if child_base.flags.contains(CLEARS_RIGHT) {
+                    right_float_width = Au::max(right_float_width, right_float_width_accumulator);
+                    right_float_width_accumulator = Au(0)
+                }
+
                 match float_kind {
                     float::T::none => {
                         computation.content_intrinsic_sizes.preferred_inline_size =
@@ -1484,11 +1493,11 @@ impl Flow for BlockFlow {
                                 child_base.intrinsic_inline_sizes.preferred_inline_size);
                     }
                     float::T::left => {
-                        left_float_width = left_float_width +
+                        left_float_width_accumulator = left_float_width_accumulator +
                             child_base.intrinsic_inline_sizes.preferred_inline_size;
                     }
                     float::T::right => {
-                        right_float_width = right_float_width +
+                        right_float_width_accumulator = right_float_width_accumulator +
                             child_base.intrinsic_inline_sizes.preferred_inline_size;
                     }
                 }
@@ -1500,6 +1509,8 @@ impl Flow for BlockFlow {
         // FIXME(pcwalton): This should consider all float descendants, not just children.
         // FIXME(pcwalton): This is not well-spec'd; INTRINSIC specifies to do this, but CSS-SIZING
         // says not to. In practice, Gecko and WebKit both do this.
+        left_float_width = Au::max(left_float_width, left_float_width_accumulator);
+        right_float_width = Au::max(right_float_width, right_float_width_accumulator);
         computation.content_intrinsic_sizes.preferred_inline_size =
             max(computation.content_intrinsic_sizes.preferred_inline_size,
                 left_float_width + right_float_width);
diff --git a/components/layout/construct.rs b/components/layout/construct.rs
index c72de1d122a..c0480e8562c 100644
--- a/components/layout/construct.rs
+++ b/components/layout/construct.rs
@@ -822,7 +822,7 @@ impl<'a> FlowConstructor<'a> {
                 block_flow));
         let fragment = Fragment::new(node, fragment_info);
 
-        let mut fragment_accumulator = InlineFragmentsAccumulator::from_inline_node(node);
+        let mut fragment_accumulator = InlineFragmentsAccumulator::new();
         fragment_accumulator.fragments.push_back(fragment);
 
         let construction_item =
diff --git a/components/layout/fragment.rs b/components/layout/fragment.rs
index 8b60b4cfc72..7ad0e8895ad 100644
--- a/components/layout/fragment.rs
+++ b/components/layout/fragment.rs
@@ -882,8 +882,7 @@ impl Fragment {
             SpecificFragmentInfo::Generic |
             SpecificFragmentInfo::GeneratedContent(_) |
             SpecificFragmentInfo::Iframe(_) |
-            SpecificFragmentInfo::Image(_) |
-            SpecificFragmentInfo::InlineBlock(_) => {
+            SpecificFragmentInfo::Image(_) => {
                 QuantitiesIncludedInIntrinsicInlineSizes::all()
             }
             SpecificFragmentInfo::Table | SpecificFragmentInfo::TableCell => {
@@ -918,7 +917,8 @@ impl Fragment {
             SpecificFragmentInfo::ScannedText(_) |
             SpecificFragmentInfo::TableColumn(_) |
             SpecificFragmentInfo::UnscannedText(_) |
-            SpecificFragmentInfo::InlineAbsoluteHypothetical(_) => {
+            SpecificFragmentInfo::InlineAbsoluteHypothetical(_) |
+            SpecificFragmentInfo::InlineBlock(_) => {
                 QuantitiesIncludedInIntrinsicInlineSizes::empty()
             }
         }
diff --git a/tests/ref/basic.list b/tests/ref/basic.list
index 5409dba1486..4d54d502ec8 100644
--- a/tests/ref/basic.list
+++ b/tests/ref/basic.list
@@ -115,6 +115,7 @@ flaky_cpu == append_style_a.html append_style_b.html
 == first_of_type_pseudo_a.html first_of_type_pseudo_b.html
 == fixed_width_overrides_child_intrinsic_width_a.html fixed_width_overrides_child_intrinsic_width_ref.html
 == float_clearance_a.html float_clearance_ref.html
+== float_clearance_intrinsic_width_a.html float_clearance_intrinsic_width_ref.html
 == float_intrinsic_height.html float_intrinsic_height_ref.html
 == float_intrinsic_width_a.html float_intrinsic_width_ref.html
 == float_right_intrinsic_width_a.html float_right_intrinsic_width_ref.html
@@ -161,6 +162,7 @@ flaky_cpu == append_style_a.html append_style_b.html
 != inline_background_a.html inline_background_ref.html
 == inline_block_baseline_a.html inline_block_baseline_ref.html
 == inline_block_border_a.html inline_block_border_ref.html
+== inline_block_border_intrinsic_size_a.html inline_block_border_intrinsic_size_ref.html
 == inline_block_img_a.html inline_block_img_ref.html
 == inline_block_margin_a.html inline_block_margin_ref.html
 == inline_block_min_width.html inline_block_min_width_ref.html
diff --git a/tests/ref/float_clearance_intrinsic_width_a.html b/tests/ref/float_clearance_intrinsic_width_a.html
new file mode 100644
index 00000000000..2e9704a5914
--- /dev/null
+++ b/tests/ref/float_clearance_intrinsic_width_a.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#nav-your-account {
+	background: lightblue;
+	display: inline-block;
+}
+.nav-button-title {
+	float: left;
+	clear: both;
+}
+</style>
+</head>
+<body>
+	<a id="nav-your-account">
+		<div class="nav-button-title">Hello.</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+	</a>
+</body>
+</html>
diff --git a/tests/ref/float_clearance_intrinsic_width_ref.html b/tests/ref/float_clearance_intrinsic_width_ref.html
new file mode 100644
index 00000000000..3d498ea2b87
--- /dev/null
+++ b/tests/ref/float_clearance_intrinsic_width_ref.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#nav-your-account {
+	background: lightblue;
+	display: inline-block;
+}
+</style>
+</head>
+<body>
+	<a id="nav-your-account">
+		<div class="nav-button-title">Hello.</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+		<div class="nav-button-title">Account</div>
+	</a>
+</body>
+</html>
diff --git a/tests/ref/inline_block_border_intrinsic_size_a.html b/tests/ref/inline_block_border_intrinsic_size_a.html
new file mode 100644
index 00000000000..7e8a7e0be19
--- /dev/null
+++ b/tests/ref/inline_block_border_intrinsic_size_a.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+html, body {
+    margin: 0;
+    font-size: 0;
+    line-height: 0;
+}
+.nav-button-outer {
+	background: red;
+	display: inline-block;
+}
+.nav-down-arrow {
+	display: inline-block;
+	border-style: solid;
+	border-color: black;
+	border-width: 10px 200px 0 0;
+}
+</style>
+</head>
+
+<body>
+	<a class="nav-button-outer"><span class="nav-down-arrow"></span></a>
+</body>
+</html>
diff --git a/tests/ref/inline_block_border_intrinsic_size_ref.html b/tests/ref/inline_block_border_intrinsic_size_ref.html
new file mode 100644
index 00000000000..b11fd4f1b8e
--- /dev/null
+++ b/tests/ref/inline_block_border_intrinsic_size_ref.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+html, body {
+    margin: 0;
+    font-size: 0;
+    line-height: 0;
+}
+.nav-button-outer {
+	display: inline-block;
+}
+.nav-down-arrow {
+	display: inline-block;
+	border-style: solid;
+	border-color: black;
+	border-width: 10px 200px 0 0;
+}
+</style>
+</head>
+
+<body>
+	<a class="nav-button-outer"><span class="nav-down-arrow"></span></a>
+</body>
+</html>