diff --git a/Userland/Libraries/LibC/mman.cpp b/Userland/Libraries/LibC/mman.cpp
index 0f01395ab5..b44c1a6803 100644
--- a/Userland/Libraries/LibC/mman.cpp
+++ b/Userland/Libraries/LibC/mman.cpp
@@ -35,7 +35,7 @@ extern "C" {
 void* serenity_mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset, size_t alignment, const char* name)
 {
     Syscall::SC_mmap_params params { (uintptr_t)addr, size, alignment, prot, flags, fd, offset, { name, name ? strlen(name) : 0 } };
-    ssize_t rc = syscall(SC_mmap, &params);
+    ptrdiff_t rc = syscall(SC_mmap, &params);
     if (rc < 0 && -rc < EMAXERRNO) {
         errno = -rc;
         return MAP_FAILED;
@@ -56,7 +56,7 @@ void* mmap_with_name(void* addr, size_t size, int prot, int flags, int fd, off_t
 void* mremap(void* old_address, size_t old_size, size_t new_size, int flags)
 {
     Syscall::SC_mremap_params params { (uintptr_t)old_address, old_size, new_size, flags };
-    ssize_t rc = syscall(SC_mremap, &params);
+    ptrdiff_t rc = syscall(SC_mremap, &params);
     if (rc < 0 && -rc < EMAXERRNO) {
         errno = -rc;
         return MAP_FAILED;
@@ -95,7 +95,7 @@ int madvise(void* address, size_t size, int advice)
 
 void* allocate_tls(size_t size)
 {
-    int rc = syscall(SC_allocate_tls, size);
+    ptrdiff_t rc = syscall(SC_allocate_tls, size);
     if (rc < 0 && -rc < EMAXERRNO) {
         errno = -rc;
         return MAP_FAILED;
diff --git a/Userland/Libraries/LibC/netdb.cpp b/Userland/Libraries/LibC/netdb.cpp
index 881e1beffe..2450d0a0e9 100644
--- a/Userland/Libraries/LibC/netdb.cpp
+++ b/Userland/Libraries/LibC/netdb.cpp
@@ -132,7 +132,7 @@ hostent* gethostbyname(const char* name)
         i32 message_id;
         i32 name_length;
     } request_header = {
-        sizeof(request_header) - sizeof(request_header.message_size) + name_length,
+        (u32)(sizeof(request_header) - sizeof(request_header.message_size) + name_length),
         lookup_server_endpoint_magic,
         1,
         (i32)name_length,
diff --git a/Userland/Libraries/LibC/scanf.cpp b/Userland/Libraries/LibC/scanf.cpp
index 7ec13da4ee..13f306d5aa 100644
--- a/Userland/Libraries/LibC/scanf.cpp
+++ b/Userland/Libraries/LibC/scanf.cpp
@@ -512,61 +512,61 @@ extern "C" int vsscanf(const char* input, const char* format, va_list ap)
             dbgln("Invalid conversion specifier {} in scanf!", (int)conversion_specifier);
             VERIFY_NOT_REACHED();
         case Decimal:
-            if (!read_element<int, ReadKind::Normal> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<int, ReadKind::Normal> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case Integer:
-            if (!read_element<int, ReadKind::Infer> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<int, ReadKind::Infer> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case Octal:
-            if (!read_element<unsigned, ReadKind::Octal> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<unsigned, ReadKind::Octal> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case Unsigned:
-            if (!read_element<unsigned, ReadKind::Normal> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<unsigned, ReadKind::Normal> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case Hex:
-            if (!read_element<unsigned, ReadKind::Hex> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<unsigned, ReadKind::Hex> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case Floating:
-            if (!read_element<float, ReadKind::Normal> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<float, ReadKind::Normal> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case String:
-            if (!read_element<char*, ReadKind::Normal> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<char*, ReadKind::Normal> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case UseScanList:
-            if (!read_element<char*, ReadKind::Normal> { scanlist, invert_scanlist }(length_modifier, input_lexer, &ap))
+            if (!read_element<char*, ReadKind::Normal> { scanlist, invert_scanlist }(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case Character:
-            if (!read_element<char, ReadKind::Normal> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<char, ReadKind::Normal> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
             break;
         case Pointer:
-            if (!read_element<void*, ReadKind::Normal> {}(length_modifier, input_lexer, &ap))
+            if (!read_element<void*, ReadKind::Normal> {}(length_modifier, input_lexer, (va_list*)&ap))
                 format_lexer.consume_all();
             else
                 ++elements_matched;
diff --git a/Userland/Libraries/LibC/serenity.cpp b/Userland/Libraries/LibC/serenity.cpp
index 8899a2b7df..1cf5f5f68f 100644
--- a/Userland/Libraries/LibC/serenity.cpp
+++ b/Userland/Libraries/LibC/serenity.cpp
@@ -73,7 +73,7 @@ int futex(uint32_t* userspace_address, int futex_op, uint32_t value, const struc
             .userspace_address = userspace_address,
             .futex_op = futex_op,
             .val = value,
-            .val2 = (uint32_t)timeout,
+            .val2 = (FlatPtr)timeout,
             .userspace_address2 = userspace_address2,
             .val3 = value3
         };