diff --git a/src/material-experimental/mdc-snack-bar/snack-bar-container.scss b/src/material-experimental/mdc-snack-bar/snack-bar-container.scss
index 40f7a3a1a2d8..c2040185fbf4 100644
--- a/src/material-experimental/mdc-snack-bar/snack-bar-container.scss
+++ b/src/material-experimental/mdc-snack-bar/snack-bar-container.scss
@@ -16,6 +16,10 @@
 }
 
 // These elements need to have full width using flex layout.
-.mat-mdc-snack-bar-handset, .mat-mdc-snack-bar-container, .mat-mdc-snack-bar-label {
-  flex: 1;
+.mat-mdc-snack-bar-handset,
+.mat-mdc-snack-bar-container,
+.mat-mdc-snack-bar-label {
+  // Note that we need to include the full `flex` shorthand
+  // declaration so the container doesn't collapse on IE11.
+  flex: 1 0 auto;
 }