diff --git a/src/lib.rs b/src/lib.rs
index 469c535..d5b59ab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -190,13 +190,22 @@ impl fmt::Debug for IntervalInfo {
 
                 Ok(())
             }
-            IntervalInfo::Stepwise { min, max, step } => write!(
-                f,
-                "Stepwise from {}fps to {}fps by {}fps",
-                max.1 / max.0,
-                min.1 / min.0,
-                step.1 / step.0
-            ),
+            IntervalInfo::Stepwise { min, max, step }
+                if min.0 != 0 && max.0 != 0 && step.0 != 0 =>
+            {
+                write!(
+                    f,
+                    "Stepwise from {}fps to {}fps by {}fps",
+                    max.1 / max.0,
+                    min.1 / min.0,
+                    step.1 / step.0
+                )
+            }
+            IntervalInfo::Stepwise {
+                min: _,
+                max: _,
+                step: _,
+            } => write!(f, "Invalid stepwise interval info with 0 denominators"),
         }
     }
 }
diff --git a/src/v4l2.rs b/src/v4l2.rs
index 8aee511..caaea7c 100644
--- a/src/v4l2.rs
+++ b/src/v4l2.rs
@@ -17,10 +17,21 @@ mod ll {
 
     pub use self::v4l2_close as close;
     pub use self::v4l2_ioctl as ioctl;
-    pub use self::v4l2_mmap as mmap;
     pub use self::v4l2_munmap as munmap;
     pub use self::v4l2_open as open;
 
+    pub unsafe fn mmap(
+        start: *mut c_void,
+        length: size_t,
+        prot: c_int,
+        flags: c_int,
+        fd: RawFd,
+        offset: off_t,
+    ) -> *mut c_void {
+        // Note the subtle function signature mismatch between mmap and v4l2_mmap.
+        v4l2_mmap(start, length, prot, flags, fd, offset as i64)
+    }
+
     #[link(name = "v4l2")]
     extern "C" {
         pub fn v4l2_open(file: *const c_char, flags: c_int, arg: c_int) -> RawFd;
@@ -32,7 +43,7 @@ mod ll {
             prot: c_int,
             flags: c_int,
             fd: RawFd,
-            offset: off_t,
+            offset: i64,
         ) -> *mut c_void;
         pub fn v4l2_munmap(start: *mut c_void, length: size_t) -> c_int;
     }
@@ -40,10 +51,21 @@ mod ll {
 
 #[cfg(feature = "no_wrapper")]
 mod ll {
-    use libc::{c_int, c_ulong, c_void};
+    use libc::{c_int, c_ulong, c_void, off_t, size_t};
     use std::os::unix::io::RawFd;
 
-    pub use libc::{close, mmap, munmap, open};
+    pub use libc::{close, munmap, open};
+
+    pub unsafe fn mmap(
+        start: *mut c_void,
+        length: size_t,
+        prot: c_int,
+        flags: c_int,
+        fd: RawFd,
+        offset: off_t,
+    ) -> *mut c_void {
+        libc::mmap(start, length, prot, flags, fd, offset)
+    }
 
     extern "C" {
         pub fn ioctl(fd: RawFd, request: c_ulong, argp: *mut c_void) -> c_int;