diff --git a/src/client/linux/minidump_writer/linux_dumper.cc b/src/client/linux/minidump_writer/linux_dumper.cc
index 5187120f..4a4b5e72 100644
--- a/src/client/linux/minidump_writer/linux_dumper.cc
+++ b/src/client/linux/minidump_writer/linux_dumper.cc
@@ -204,7 +204,7 @@ LinuxDumper::BuildProcPath(char* path, pid_t pid, const char* node) const {
 
 bool
 LinuxDumper::ElfFileIdentifierForMapping(const MappingInfo& mapping,
-                                         unsigned int mapping_id,
+                                         int mapping_id,
                                          uint8_t identifier[sizeof(MDGUID)])
 {
   assert(mapping_id == -1 || mapping_id < mappings_.size());
diff --git a/src/client/linux/minidump_writer/linux_dumper.h b/src/client/linux/minidump_writer/linux_dumper.h
index 2233ec05..c1126a1f 100644
--- a/src/client/linux/minidump_writer/linux_dumper.h
+++ b/src/client/linux/minidump_writer/linux_dumper.h
@@ -154,7 +154,7 @@ class LinuxDumper {
   // Generate a File ID from the .text section of a mapped entry.
   // mapping_id may be -1 if this is not a member of mappings_.
   bool ElfFileIdentifierForMapping(const MappingInfo& mapping,
-                                   unsigned int mapping_id,
+                                   int mapping_id,
                                    uint8_t identifier[sizeof(MDGUID)]);
 
   // Utility method to find the location of where the kernel has
diff --git a/src/client/linux/minidump_writer/minidump_writer.cc b/src/client/linux/minidump_writer/minidump_writer.cc
index 3eb90953..10084ac4 100644
--- a/src/client/linux/minidump_writer/minidump_writer.cc
+++ b/src/client/linux/minidump_writer/minidump_writer.cc
@@ -820,10 +820,9 @@ class MinidumpWriter {
 
   // Fill the MDRawModule |mod| with information about the provided
   // |mapping|. If |identifier| is non-NULL, use it instead of calculating
-  // a file ID from the mapping. |mapping_id| can be -1 if this mapping
-  // is not from the LinuxDumper.
+  // a file ID from the mapping. |mapping_id| can be -1.
   bool FillRawModule(const MappingInfo& mapping,
-                     unsigned int mapping_id,
+                     int mapping_id,
                      MDRawModule& mod,
                      const u_int8_t* identifier) {
     my_memset(&mod, 0, MD_MODULE_SIZE);