diff --git a/src/CodecZlib.jl b/src/CodecZlib.jl
index 2b68193..685ad99 100644
--- a/src/CodecZlib.jl
+++ b/src/CodecZlib.jl
@@ -39,6 +39,11 @@ function splitkwargs(kwargs, keys)
     return hits, others
 end
 
+# For compatibility.
+if !isdefined(Base, :Cvoid)
+    const Cvoid = Void
+end
+
 include("libz.jl")
 include("compression.jl")
 include("decompression.jl")
diff --git a/src/libz.jl b/src/libz.jl
index e829d45..a1de796 100644
--- a/src/libz.jl
+++ b/src/libz.jl
@@ -11,11 +11,11 @@ mutable struct ZStream
     total_out::Culong
 
     msg::Ptr{UInt8}
-    state::Ptr{Void}
+    state::Ptr{Cvoid}
 
-    zalloc::Ptr{Void}
-    zfree::Ptr{Void}
-    opaque::Ptr{Void}
+    zalloc::Ptr{Cvoid}
+    zfree::Ptr{Cvoid}
+    opaque::Ptr{Cvoid}
 
     data_type::Cint