diff --git a/browser/themes/linux/devtools/debugger.css b/browser/themes/linux/devtools/debugger.css
index 2cbee25a5dbd..ee736ec8fd85 100644
--- a/browser/themes/linux/devtools/debugger.css
+++ b/browser/themes/linux/devtools/debugger.css
@@ -5,6 +5,10 @@
 
 /* Sources and breakpoints pane */
 
+#sources-pane {
+  min-width: 50px;
+}
+
 #sources-pane > tabs {
   -moz-border-end: 1px solid #222426; /* Match the sources list's dark margin. */
 }
@@ -68,8 +72,7 @@
 #black-boxed-message,
 #source-progress-container {
   background: url(background-noise-toolbar.png) rgb(61,69,76);
-  /* Prevent the container deck from aquiring the size from this message. */
-  min-width: 1px;
+  /* Prevent the container deck from aquiring the height from this message. */
   min-height: 1px;
   color: white;
 }
diff --git a/browser/themes/linux/devtools/widgets.css b/browser/themes/linux/devtools/widgets.css
index 626a53bcb39c..8342525997d9 100644
--- a/browser/themes/linux/devtools/widgets.css
+++ b/browser/themes/linux/devtools/widgets.css
@@ -6,6 +6,7 @@
 /* Generic pane helpers */
 
 .generic-toggled-side-pane {
+  min-width: 50px;
   -moz-margin-start: 0px !important;
   /* Unfortunately, transitions don't work properly with locale-aware properties,
      so both the left and right margins are set via js, while the start margin
diff --git a/browser/themes/osx/devtools/debugger.css b/browser/themes/osx/devtools/debugger.css
index ffcb34e03397..55dfeee48bde 100644
--- a/browser/themes/osx/devtools/debugger.css
+++ b/browser/themes/osx/devtools/debugger.css
@@ -7,6 +7,10 @@
 
 /* Sources and breakpoints pane */
 
+#sources-pane {
+  min-width: 50px;
+}
+
 #sources-pane > tabs {
   -moz-border-end: 1px solid #222426; /* Match the sources list's dark margin. */
 }
@@ -70,8 +74,7 @@
 #black-boxed-message,
 #source-progress-container {
   background: url(background-noise-toolbar.png) rgb(61,69,76);
-  /* Prevent the container deck from aquiring the size from this message. */
-  min-width: 1px;
+  /* Prevent the container deck from aquiring the height from this message. */
   min-height: 1px;
   color: white;
 }
diff --git a/browser/themes/osx/devtools/widgets.css b/browser/themes/osx/devtools/widgets.css
index d4ba3b294628..6b8b33893f60 100644
--- a/browser/themes/osx/devtools/widgets.css
+++ b/browser/themes/osx/devtools/widgets.css
@@ -6,6 +6,7 @@
 /* Generic pane helpers */
 
 .generic-toggled-side-pane {
+  min-width: 50px;
   -moz-margin-start: 0px !important;
   /* Unfortunately, transitions don't work properly with locale-aware properties,
      so both the left and right margins are set via js, while the start margin
diff --git a/browser/themes/windows/devtools/debugger.css b/browser/themes/windows/devtools/debugger.css
index 0087c30aafea..6343a0fd5a40 100644
--- a/browser/themes/windows/devtools/debugger.css
+++ b/browser/themes/windows/devtools/debugger.css
@@ -5,6 +5,10 @@
 
 /* Sources and breakpoints pane */
 
+#sources-pane {
+  min-width: 50px;
+}
+
 #sources-pane > tabs {
   -moz-border-end: 1px solid #222426; /* Match the sources list's dark margin. */
 }
@@ -68,8 +72,7 @@
 #black-boxed-message,
 #source-progress-container {
   background: url(background-noise-toolbar.png) rgb(61,69,76);
-  /* Prevent the container deck from aquiring the size from this message. */
-  min-width: 1px;
+  /* Prevent the container deck from aquiring the height from this message. */
   min-height: 1px;
   color: white;
 }
diff --git a/browser/themes/windows/devtools/widgets.css b/browser/themes/windows/devtools/widgets.css
index 10a3c7c973e3..e154432dd754 100644
--- a/browser/themes/windows/devtools/widgets.css
+++ b/browser/themes/windows/devtools/widgets.css
@@ -6,6 +6,7 @@
 /* Generic pane helpers */
 
 .generic-toggled-side-pane {
+  min-width: 50px;
   -moz-margin-start: 0px !important;
   /* Unfortunately, transitions don't work properly with locale-aware properties,
      so both the left and right margins are set via js, while the start margin