diff --git a/src/codegen/sys/lib_.rs b/src/codegen/sys/lib_.rs
index 87c05ef35..65d0d5bdd 100644
--- a/src/codegen/sys/lib_.rs
+++ b/src/codegen/sys/lib_.rs
@@ -312,6 +312,7 @@ fn generate_enums(w: &mut Write, env: &Env, items: &[&Enumeration]) -> Result<()
 }
 
 fn generate_unions(w: &mut Write, env: &Env, items: &[&Union]) -> Result<()> {
+
     if !items.is_empty() {
         try!(writeln!(w, "// Unions"));
     }
@@ -363,8 +364,11 @@ fn generate_unions(w: &mut Write, env: &Env, items: &[&Union]) -> Result<()> {
             }
         }
     }
-    if !items.is_empty() {
-        try!(writeln!(w, ""));
+    #[cfg(not(feature = "use_unions"))]
+    {
+        if !items.is_empty() {
+            try!(writeln!(w, ""));
+        }
     }
 
     Ok(())
@@ -530,7 +534,7 @@ fn generate_fields(env: &Env, struct_name: &str, fields: &[Field]) -> (Vec<Strin
             }
         }
 
-        if !cfg!(feature = "use_unions") || is_bits {
+        if !cfg!(feature = "use_unions") || (is_bits && !truncated) {
             if !is_gweakref && !truncated && !is_ptr &&
                 (is_union || is_bits) &&
                 !is_union_special_case(&field.c_type)
@@ -543,24 +547,24 @@ fn generate_fields(env: &Env, struct_name: &str, fields: &[Field]) -> (Vec<Strin
                 lines.push("\t_truncated_record_marker: c_void,".to_owned());
                 truncated = true;
             }
+        }
 
-            if truncated {
-                if is_union {
-                    lines.push("\t//union,".to_owned());
-                } else {
-                    let bits = field
-                        .bits
-                        .map(|n| format!(": {}", n))
-                        .unwrap_or_else(|| "".to_owned());
-                    lines.push(format!(
-                        "\t//{}: {}{},",
-                        field.name,
-                        field.c_type.as_ref().map(|s| &s[..]).unwrap_or("fn"),
-                        bits
-                    ));
-                };
-                continue 'fields;
-            }
+        if truncated {
+            if is_union {
+                lines.push("\t//union,".to_owned());
+            } else {
+                let bits = field
+                    .bits
+                    .map(|n| format!(": {}", n))
+                    .unwrap_or_else(|| "".to_owned());
+                lines.push(format!(
+                    "\t//{}: {}{},",
+                    field.name,
+                    field.c_type.as_ref().map(|s| &s[..]).unwrap_or("fn"),
+                    bits
+                ));
+            };
+            continue 'fields;
         }
 
         if let Some(ref c_type) = field.c_type {