--- a/devtools/client/aboutdebugging/aboutdebugging.css
+++ b/devtools/client/aboutdebugging/aboutdebugging.css
@@ -56,17 +56,17 @@ button {
   padding: 0;
 }
 
 .target-container {
   margin-top: 5px;
   min-height: 34px;
   display: flex;
   flex-direction: row;
-  align-items: self-start;
+  align-items: start;
 }
 
 .target-icon {
   height: 24px;
   margin: 0 5px 0 0;
 }
 
 .target-icon:not([src]) {

--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -2873,17 +2873,17 @@ CrossAxisPositionTracker::
   // past any leading packing-space.
   if (mPackingSpaceRemaining != 0) {
     switch (mAlignContent) {
       case NS_STYLE_ALIGN_SELF_START:
       case NS_STYLE_ALIGN_SELF_END:
       case NS_STYLE_ALIGN_SPACE_EVENLY:
       case NS_STYLE_ALIGN_BASELINE:
       case NS_STYLE_ALIGN_LAST_BASELINE:
-        NS_WARNING("NYI: align-self:left/right/self-start/self-end/space-evenly/baseline/last-baseline");
+        NS_WARNING("NYI: align-items/align-self:left/right/self-start/self-end/space-evenly/baseline/last-baseline");
         MOZ_FALLTHROUGH;
       case NS_STYLE_ALIGN_FLEX_START:
         // All packing space should go at the end --> nothing to do here.
         break;
       case NS_STYLE_ALIGN_FLEX_END:
         // All packing space goes at the beginning
         mPosition += mPackingSpaceRemaining;
         break;
@@ -3174,17 +3174,17 @@ SingleLineCrossAxisPositionTracker::
       alignSelf = NS_STYLE_ALIGN_FLEX_START;
     }
   }
 
   switch (alignSelf) {
     case NS_STYLE_ALIGN_SELF_START:
     case NS_STYLE_ALIGN_SELF_END:
     case NS_STYLE_ALIGN_LAST_BASELINE:
-      NS_WARNING("NYI: align-self:left/right/self-start/self-end/last-baseline");
+      NS_WARNING("NYI: align-items/align-self:left/right/self-start/self-end/last-baseline");
       MOZ_FALLTHROUGH;
     case NS_STYLE_ALIGN_FLEX_START:
       // No space to skip over -- we're done.
       break;
     case NS_STYLE_ALIGN_FLEX_END:
       mPosition += aLine.GetLineCrossSize() - aItem.GetOuterCrossSize(mAxis);
       break;
     case NS_STYLE_ALIGN_CENTER: