diff --git a/DESCRIPTION b/DESCRIPTION
index 47beeec0..fd1a69a2 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: profvis
 Title: Interactive Visualizations for Profiling R Code
-Version: 0.3.4
+Version: 0.3.4.9000
 Authors@R: c(
     person("Winston", "Chang", email = "winston@rstudio.com", role = c("aut", "cre")),
     person("Javier", "Luraschi", email = "javier@rstudio.com", role = "aut"),
diff --git a/NEWS.md b/NEWS.md
index 4dde6e3c..dc08421d 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,8 @@
+profvis 0.3.4.9000
+=============
+
+* Fixed problem with development build of R where source refs are turned on by defaut (reported by Tomas Kalibera).
+
 profvis 0.3.4
 =============
 
diff --git a/R/file_contents.R b/R/file_contents.R
index aa37bb85..9fd2c700 100644
--- a/R/file_contents.R
+++ b/R/file_contents.R
@@ -73,8 +73,12 @@ get_pkg_srcrefs <- function(pkg) {
   # Given a char vector with contents of an entire package, split out all
   # files into separate entries in a list.
   full_src_to_file_contents <- function(src) {
-    # Drop first line (simply contains package name)
-    src <- src[-1]
+    # Before R 2.5.0, the first line looked like this:
+    # .packageName <- "R6"
+    # As of 2.5.0, that line was dropped. If that line is present, remove it.
+    if (grepl("^\\.packageName <-", src[1])) {
+      src <- src[-1]
+    }
 
     # Lines which contain filenames. Have a format like:
     #   "#line 1 \"/tmp/Rtmp6W0MLC/R.INSTALL1a531f3beb59/ggplot2/R/aaa-.r\""