diff --git a/src/lib/expansion/expansion-animations.ts b/src/lib/expansion/expansion-animations.ts
index 47e243f9d1ee..09ac5f99b486 100644
--- a/src/lib/expansion/expansion-animations.ts
+++ b/src/lib/expansion/expansion-animations.ts
@@ -20,7 +20,26 @@ import {
 /** Time and timing curve for expansion panel animations. */
 export const EXPANSION_PANEL_ANIMATION_TIMING = '225ms cubic-bezier(0.4,0.0,0.2,1)';
 
-/** Animations used by the Material expansion panel. */
+/**
+ * Animations used by the Material expansion panel.
+ *
+ * A bug in angular animation's `state` when ViewContainers are moved using ViewContainerRef.move()
+ * causes the animation state of moved components to become `void` upon exit, and not update again
+ * upon reentry into the DOM.  This can lead a to situation for the expansion panel where the state
+ * of the panel is `expanded` or `collapsed` but the animation state is `void`.
+ *
+ * To correctly handle animating to the next state, we animate between `void` and `collapsed` which
+ * are defined to have the same styles. Since angular animates from the current styles to the
+ * destination state's style definition, in situations where we are moving from `void`'s styles to
+ * `collapsed` this acts a noop since no style values change.
+ *
+ * In the case where angular's animation state is out of sync with the expansion panel's state, the
+ * expansion panel being `expanded` and angular animations being`void`, the animation from the
+ * `expanded`'s effective styles (though in a `void` animation state) to the collapsed state will
+ * occur as expected.
+ *
+ * Angular Bug: https://github.com/angular/angular/issues/18847
+ */
 export const matExpansionAnimations: {
   readonly indicatorRotate: AnimationTriggerMetadata;
   readonly expansionHeaderHeight: AnimationTriggerMetadata;
@@ -28,14 +47,15 @@ export const matExpansionAnimations: {
 } = {
   /** Animation that rotates the indicator arrow. */
   indicatorRotate: trigger('indicatorRotate', [
-    state('collapsed', style({transform: 'rotate(0deg)'})),
+    state('collapsed, void', style({transform: 'rotate(0deg)'})),
     state('expanded', style({transform: 'rotate(180deg)'})),
-    transition('expanded <=> collapsed', animate(EXPANSION_PANEL_ANIMATION_TIMING)),
+    transition('expanded <=> collapsed, void => collapsed',
+      animate(EXPANSION_PANEL_ANIMATION_TIMING)),
   ]),
 
   /** Animation that expands and collapses the panel header height. */
   expansionHeaderHeight: trigger('expansionHeight', [
-    state('collapsed', style({
+    state('collapsed, void', style({
       height: '{{collapsedHeight}}',
     }), {
       params: {collapsedHeight: '48px'},
@@ -45,7 +65,7 @@ export const matExpansionAnimations: {
     }), {
       params: {expandedHeight: '64px'}
     }),
-    transition('expanded <=> collapsed', group([
+    transition('expanded <=> collapsed, void => collapsed', group([
       query('@indicatorRotate', animateChild(), {optional: true}),
       animate(EXPANSION_PANEL_ANIMATION_TIMING),
     ])),
@@ -53,8 +73,9 @@ export const matExpansionAnimations: {
 
   /** Animation that expands and collapses the panel content. */
   bodyExpansion: trigger('bodyExpansion', [
-    state('collapsed', style({height: '0px', visibility: 'hidden'})),
+    state('collapsed, void', style({height: '0px', visibility: 'hidden'})),
     state('expanded', style({height: '*', visibility: 'visible'})),
-    transition('expanded <=> collapsed', animate(EXPANSION_PANEL_ANIMATION_TIMING)),
+    transition('expanded <=> collapsed, void => collapsed',
+      animate(EXPANSION_PANEL_ANIMATION_TIMING)),
   ])
 };