diff --git a/labltk-8.06.4-remove-ocaml-406-isms.patch b/labltk-8.06.4-remove-ocaml-406-isms.patch
new file mode 100644
index 0000000..2800dae
--- /dev/null
+++ b/labltk-8.06.4-remove-ocaml-406-isms.patch
@@ -0,0 +1,94 @@
+diff -ur labltk-8.06.4.old/builtin/rawimg.ml labltk-8.06.4/builtin/rawimg.ml
+--- labltk-8.06.4.old/builtin/rawimg.ml	2017-10-30 09:19:07.000000000 +0000
++++ labltk-8.06.4/builtin/rawimg.ml	2018-04-17 12:31:55.769002974 +0100
+@@ -10,8 +10,6 @@
+   pixmap_data: bytes
+ }
+ 
+-let (.![]<-) = Bytes.set
+-
+ type pixel = string  (* 3 chars *)
+ 
+ (* pixmap will be an abstract type *)
+@@ -74,9 +72,9 @@
+ (* Char.chr does range checking *)
+ let pixel r g b =
+   let s = Bytes.create 3 in
+-  s.![0] <- Char.chr r;
+-  s.![1] <- Char.chr g;
+-  s.![2] <- Char.chr b;
++  Bytes.set s 0 (Char.chr r);
++  Bytes.set s 1 (Char.chr g);
++  Bytes.set s 2 (Char.chr b);
+   Bytes.unsafe_to_string s
+ 
+ ##ifdef CAMLTK
+diff -ur labltk-8.06.4.old/compiler/printer.ml labltk-8.06.4/compiler/printer.ml
+--- labltk-8.06.4.old/compiler/printer.ml	2017-10-30 09:19:07.000000000 +0000
++++ labltk-8.06.4/compiler/printer.ml	2018-04-17 12:31:55.769002974 +0100
+@@ -18,8 +18,6 @@
+ 
+ open Format;;
+ 
+-let (.![]<-) = Bytes.set ;;
+-
+ let escape_string s =
+   let more = ref 0 in
+   for i = 0 to String.length s - 1 do
+@@ -33,8 +31,12 @@
+   for i = 0 to String.length s - 1 do
+    let c = s.[i] in
+    match c with
+-   | '\\' | '\"' |'\'' -> res.![!j] <- '\\'; incr j; res.![!j] <- c; incr j
+-   | _ -> res.![!j] <- c; incr j
++   | '\\' | '\"' |'\'' ->
++     Bytes.set res !j '\\';
++     incr j;
++     Bytes.set res !j c;
++     incr j
++   | _ -> Bytes.set res !j c; incr j
+   done;
+   Bytes.to_string res
+ ;;
+diff -ur labltk-8.06.4.old/configure labltk-8.06.4/configure
+--- labltk-8.06.4.old/configure	2017-10-30 09:19:07.000000000 +0000
++++ labltk-8.06.4/configure	2018-04-17 12:51:29.609484064 +0100
+@@ -158,7 +158,7 @@
+   has_tk=true
+ fi
+ 
+-cc=`cat $where/Makefile.config | grep '^CC=' | sed -e 's/^CC=//'`
++cc=`cat $where/Makefile.config | grep '^NATIVECC=' | sed -e 's/^NATIVECC=//'`
+ cclibs=`cat $where/Makefile.config | grep '^NATIVECCLIBS=' | sed -e 's/^NATIVECCLIBS=//'`
+ export cc cclibs
+ 
+diff -ur labltk-8.06.4.old/Makefile labltk-8.06.4/Makefile
+--- labltk-8.06.4.old/Makefile	2017-10-30 09:19:07.000000000 +0000
++++ labltk-8.06.4/Makefile	2018-04-17 13:00:33.216962824 +0100
+@@ -17,7 +17,7 @@
+ # Top Makefile for mlTk
+ 
+ SUBDIRS=compiler support lib jpf frx examples_labltk \
+-	examples_camltk browser
++	examples_camltk
+ SUBDIRS_GENERATED=camltk labltk
+ include config/Makefile
+ 
+@@ -31,7 +31,7 @@
+ 	cd lib; $(MAKE)
+ 	cd jpf; $(MAKE)
+ 	cd frx; $(MAKE)
+-	cd browser; $(MAKE)
++#	cd browser; $(MAKE)
+ 
+ allopt:
+ 	cd support; $(MAKE) opt
+@@ -78,7 +78,7 @@
+ 	cd compiler; $(MAKE) install
+ 	cd jpf; $(MAKE) install
+ 	cd frx; $(MAKE) install
+-	cd browser; $(MAKE) install
++#	cd browser; $(MAKE) install
+ 	if test -f lib/labltk.cmxa; then $(MAKE) installopt; else :; fi
+ 
+ installopt:
diff --git a/ocaml-labltk.spec b/ocaml-labltk.spec
index 37cec03..8114758 100644
--- a/ocaml-labltk.spec
+++ b/ocaml-labltk.spec
@@ -19,6 +19,9 @@ Source0:       https://forge.ocamlcore.org/frs/download.php/1727/labltk-8.06.4.t
 Patch1:        labltk-8.06.0-enable-debugging.patch
 Patch2:        labltk-8.06.4-enable-more-debugging.patch
 
+# Remove some OCaml 4.06-isms.
+Patch3:        labltk-8.06.4-remove-ocaml-406-isms.patch
+
 BuildRequires: ocaml
 BuildRequires: tcl-devel, tk-devel
 
@@ -46,6 +49,7 @@ This package contains the development files.
 
 %patch1 -p1
 %patch2 -p1
+%patch3 -p1
 
 # Remove version control files which might get copied into documentation.
 find -name .gitignore -delete
@@ -94,7 +98,7 @@ install -m 0644 camltk/*.o $RPM_BUILD_ROOT%{_libdir}/ocaml/labltk
 %doc examples_camltk
 %doc examples_labltk
 %{_bindir}/labltk
-%{_bindir}/ocamlbrowser
+#%{_bindir}/ocamlbrowser
 %{_libdir}/ocaml/labltk/labltktop
 %{_libdir}/ocaml/labltk/pp
 %{_libdir}/ocaml/labltk/tkcompiler