diff --git a/rosdep.yaml b/rosdep.yaml
index 9d030b30..49b59e17 100644
--- a/rosdep.yaml
+++ b/rosdep.yaml
@@ -71,9 +71,9 @@ bzip2:
   macports: bzip2
 boost:
   ubuntu:
-    9.10: libboost1.40-all-dev
-    9.04: libboost1.37-dev
-    8.10: |
+    '9.10': libboost1.40-all-dev
+    '9.04': libboost1.37-dev
+    '8.10': |
       if [ ! -f /opt/ros/lib/libboost_date_time-gcc43-mt*-1_37.a ] ; then
         mkdir -p ~/ros/ros-deps
         cd ~/ros/ros-deps
@@ -84,7 +84,7 @@ boost:
         make
         sudo make install
       fi
-    8.04: |
+    '8.04': |
       if [ ! -f /opt/ros/lib/libboost_date_time-gcc42-mt*-1_37.a ] ; then
         mkdir -p ~/ros/ros-deps
         cd ~/ros/ros-deps
@@ -168,9 +168,9 @@ wxpython:
   macports: py25-wxpython
 log4cxx:
   ubuntu:
-    9.10: liblog4cxx10-dev
-    9.04: liblog4cxx10-dev
-    8.10: |
+    '9.10': liblog4cxx10-dev
+    '9.04': liblog4cxx10-dev
+    '8.10': |
       if [ ! -f /opt/ros/lib/liblog4cxx.so.10 ] ; then
         mkdir -p ~/ros/ros-deps
         cd ~/ros/ros-deps
@@ -181,7 +181,7 @@ log4cxx:
         make
         sudo make install
       fi
-    8.04: |
+    '8.04': |
       if [ ! -f /opt/ros/lib/liblog4cxx.so.10 ] ; then
         mkdir -p ~/ros/ros-deps
         cd ~/ros/ros-deps
@@ -286,10 +286,10 @@ automake:
   macports: automake
 libtool:
   ubuntu: 
-    9.10: libtool libltdl-dev
-    9.04: libtool libltdl7-dev
-    8.10: libtool libltdl7-dev
-    8.04: libtool libltdl3-dev
+    '9.10': libtool libltdl-dev
+    '9.04': libtool libltdl7-dev
+    '8.10': libtool libltdl7-dev
+    '8.04': libtool libltdl3-dev
   debian: libtool libltdl3-dev
   fedora: libtool libtool-ltdl-devel
   rhel: libtool libtool-ltdl-devel
diff --git a/tools/rosdep/src/rosdep/core.py b/tools/rosdep/src/rosdep/core.py
index 722a1cf6..944542e9 100644
--- a/tools/rosdep/src/rosdep/core.py
+++ b/tools/rosdep/src/rosdep/core.py
@@ -187,6 +187,7 @@ class RosdepLookupPackage:
                     if self.os_name == "ubuntu" and float(key) == float(self.os_version):
                         #print "Matched %s"%(os_version)
                         # NOTE: this hack fails if os_version is not major.minor
+                        print >> sys.stderr, "Warning: Ubuntu versions should be specified as a string not as a float, e.g. convert %.2f to '%.2f'.\n Please update '%s'"%(float(self.os_version), float(self.os_version), os_specific)
                         return os_specific[key]
                 print >> sys.stderr, "failed to find specific version %s of %s within"%(self.os_version, self.os_name), os_specific
                 return False