diff --git a/src/unix/notbsd/linux/mips/mod.rs b/src/unix/notbsd/linux/mips/mod.rs
index 833a3210..4c14d12e 100644
--- a/src/unix/notbsd/linux/mips/mod.rs
+++ b/src/unix/notbsd/linux/mips/mod.rs
@@ -21,11 +21,16 @@ s! {
     }
 
     // FIXME this is actually a union
+    #[cfg_attr(all(feature = "align", target_pointer_width = "32"),
+               repr(align(4)))]
+    #[cfg_attr(all(feature = "align", target_pointer_width = "64"),
+               repr(align(8)))]
     pub struct sem_t {
         #[cfg(target_pointer_width = "32")]
         __size: [::c_char; 16],
         #[cfg(target_pointer_width = "64")]
         __size: [::c_char; 32],
+        #[cfg(not(feature = "align"))]
         __align: [::c_long; 0],
     }
 
diff --git a/src/unix/notbsd/linux/other/mod.rs b/src/unix/notbsd/linux/other/mod.rs
index 6a326dd2..93b710b8 100644
--- a/src/unix/notbsd/linux/other/mod.rs
+++ b/src/unix/notbsd/linux/other/mod.rs
@@ -158,11 +158,16 @@ s! {
     }
 
     // FIXME this is actually a union
+    #[cfg_attr(all(feature = "align", target_pointer_width = "32"),
+               repr(align(4)))]
+    #[cfg_attr(all(feature = "align", target_pointer_width = "64"),
+               repr(align(8)))]
     pub struct sem_t {
         #[cfg(target_pointer_width = "32")]
         __size: [::c_char; 16],
         #[cfg(target_pointer_width = "64")]
         __size: [::c_char; 32],
+        #[cfg(not(feature = "align"))]
         __align: [::c_long; 0],
     }
 
diff --git a/src/unix/notbsd/linux/s390x.rs b/src/unix/notbsd/linux/s390x.rs
index 61745a36..5593222e 100644
--- a/src/unix/notbsd/linux/s390x.rs
+++ b/src/unix/notbsd/linux/s390x.rs
@@ -245,8 +245,13 @@ s! {
     }
 
     // FIXME this is actually a union
+    #[cfg_attr(all(feature = "align", target_pointer_width = "32"),
+               repr(align(4)))]
+    #[cfg_attr(all(feature = "align", target_pointer_width = "64"),
+               repr(align(8)))]
     pub struct sem_t {
         __size: [::c_char; 32],
+        #[cfg(not(feature = "align"))]
         __align: [::c_long; 0],
     }
 
diff --git a/src/unix/uclibc/mips/mips32.rs b/src/unix/uclibc/mips/mips32.rs
index 7ad547c0..dcbfcf8f 100644
--- a/src/unix/uclibc/mips/mips32.rs
+++ b/src/unix/uclibc/mips/mips32.rs
@@ -222,11 +222,16 @@ s! {
     }
 
     // FIXME this is actually a union
+    #[cfg_attr(all(feature = "align", target_pointer_width = "32"),
+               repr(align(4)))]
+    #[cfg_attr(all(feature = "align", target_pointer_width = "64"),
+               repr(align(8)))]
     pub struct sem_t {
         #[cfg(target_pointer_width = "32")]
         __size: [::c_char; 16],
         #[cfg(target_pointer_width = "64")]
         __size: [::c_char; 32],
+        #[cfg(not(feature = "align"))]
         __align: [::c_long; 0],
     }
 }
diff --git a/src/unix/uclibc/mips/mips64.rs b/src/unix/uclibc/mips/mips64.rs
index 79bac1fa..e35938b1 100644
--- a/src/unix/uclibc/mips/mips64.rs
+++ b/src/unix/uclibc/mips/mips64.rs
@@ -188,8 +188,13 @@ s! {
     }
 
     // FIXME this is actually a union
+    #[cfg_attr(all(feature = "align", target_pointer_width = "32"),
+               repr(align(4)))]
+    #[cfg_attr(all(feature = "align", target_pointer_width = "64"),
+               repr(align(8)))]
     pub struct sem_t {
         __size: [::c_char; 32],
+        #[cfg(not(feature = "align"))]
         __align: [::c_long; 0],
     }
 }
diff --git a/src/unix/uclibc/x86_64/mod.rs b/src/unix/uclibc/x86_64/mod.rs
index a8d58543..dac91077 100644
--- a/src/unix/uclibc/x86_64/mod.rs
+++ b/src/unix/uclibc/x86_64/mod.rs
@@ -205,11 +205,16 @@ s! {
         pub c_cc: [::cc_t; ::NCCS],
     }
 
+    #[cfg_attr(all(feature = "align", target_pointer_width = "32"),
+               repr(align(4)))]
+    #[cfg_attr(all(feature = "align", target_pointer_width = "64"),
+               repr(align(8)))]
     pub struct sem_t { // ToDo
         #[cfg(target_pointer_width = "32")]
         __size: [::c_char; 16],
         #[cfg(target_pointer_width = "64")]
         __size: [::c_char; 32],
+        #[cfg(not(feature = "align"))]
         __align: [::c_long; 0],
     }