diff --git a/appveyor.yml b/appveyor.yml
index f0589b0e64561..c662ba0360254 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -35,13 +35,13 @@ environment:
     RUST_CONFIGURE_ARGS: --build=i686-pc-windows-gnu --enable-ninja
     SCRIPT: python x.py test
     MINGW_URL: https://s3.amazonaws.com/rust-lang-ci/rust-ci-mirror
-    MINGW_ARCHIVE: i686-6.2.0-release-posix-dwarf-rt_v5-rev1.7z
+    MINGW_ARCHIVE: i686-6.3.0-release-posix-dwarf-rt_v5-rev2.7z
     MINGW_DIR: mingw32
   - MSYS_BITS: 64
     SCRIPT: python x.py test
     RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu --enable-ninja
     MINGW_URL: https://s3.amazonaws.com/rust-lang-ci/rust-ci-mirror
-    MINGW_ARCHIVE: x86_64-6.2.0-release-posix-seh-rt_v5-rev1.7z
+    MINGW_ARCHIVE: x86_64-6.3.0-release-posix-seh-rt_v5-rev2.7z
     MINGW_DIR: mingw64
 
   # 32/64 bit MSVC and GNU deployment
@@ -60,14 +60,14 @@ environment:
     RUST_CONFIGURE_ARGS: --build=i686-pc-windows-gnu --enable-extended --enable-ninja
     SCRIPT: python x.py dist
     MINGW_URL: https://s3.amazonaws.com/rust-lang-ci/rust-ci-mirror
-    MINGW_ARCHIVE: i686-6.2.0-release-posix-dwarf-rt_v5-rev1.7z
+    MINGW_ARCHIVE: i686-6.3.0-release-posix-dwarf-rt_v5-rev2.7z
     MINGW_DIR: mingw32
     DEPLOY: 1
   - MSYS_BITS: 64
     SCRIPT: python x.py dist
     RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-gnu --enable-extended --enable-ninja
     MINGW_URL: https://s3.amazonaws.com/rust-lang-ci/rust-ci-mirror
-    MINGW_ARCHIVE: x86_64-6.2.0-release-posix-seh-rt_v5-rev1.7z
+    MINGW_ARCHIVE: x86_64-6.3.0-release-posix-seh-rt_v5-rev2.7z
     MINGW_DIR: mingw64
     DEPLOY: 1
 
@@ -96,6 +96,26 @@ install:
   - if defined MINGW_URL 7z x -y %MINGW_ARCHIVE% > nul
   - if defined MINGW_URL set PATH=%CD%\%MINGW_DIR%\bin;C:\msys64\usr\bin;%PATH%
 
+  # Here we do a pretty heinous thing which is to mangle the MinGW installation
+  # we just had above. Currently, as of this writing, we're using MinGW-w64
+  # builds of gcc, and that's currently at 6.3.0. We use 6.3.0 as it appears to
+  # be the first version which contains a fix for #40546, builds randomly
+  # failing during LLVM due to ar.exe/ranlib.exe failures.
+  #
+  # Unfortunately, though, 6.3.0 *also* is the first version of MinGW-w64 builds
+  # to contain a regression in gdb (#40184). As a result if we were to use the
+  # gdb provided (7.11.1) then we would fail all debuginfo tests.
+  #
+  # In order to fix spurious failures (pretty high priority) we use 6.3.0. To
+  # avoid disabling gdb tests we download an *old* version of gdb, specifically
+  # that found inside the 6.2.0 distribution. We then overwrite the 6.3.0 gdb
+  # with the 6.2.0 gdb to get tests passing.
+  #
+  # Note that we don't literally overwrite the gdb.exe binary because it appears
+  # to just use gdborig.exe, so that's the binary we deal with instead.
+  - if defined MINGW_URL appveyor-retry appveyor DownloadFile %MINGW_URL%/2017-04-20-%MSYS_BITS%bit-gdborig.exe
+  - if defined MINGW_URL mv 2017-04-20-%MSYS_BITS%bit-gdborig.exe %MINGW_DIR%\bin\gdborig.exe
+
   # Otherwise pull in the MinGW installed on appveyor
   - if NOT defined MINGW_URL set PATH=C:\msys64\mingw%MSYS_BITS%\bin;C:\msys64\usr\bin;%PATH%