diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index cd94fa05845..60b008c2bd5 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -6498,6 +6498,7 @@ ast_process_struct_or_iface_block_members(exec_list *instructions,
                                       "must be a multiple of the base "
                                       "alignment of %s", field_type->name);
                   }
+                  fields[i].offset = qual_offset;
                   next_offset = glsl_align(qual_offset + size, align);
                } else {
                   _mesa_glsl_error(&loc, state, "offset can only be used "
@@ -6505,6 +6506,7 @@ ast_process_struct_or_iface_block_members(exec_list *instructions,
                }
             }
          } else {
+            fields[i].offset = -1;
             if (align != 0 && size != 0)
                next_offset = glsl_align(next_offset + size, align);
          }
@@ -6883,6 +6885,8 @@ ast_interface_block::hir(exec_list *instructions,
          } else {
             fields[i].location =
                earlier_per_vertex->fields.structure[j].location;
+            fields[i].offset =
+               earlier_per_vertex->fields.structure[j].offset;
             fields[i].interpolation =
                earlier_per_vertex->fields.structure[j].interpolation;
             fields[i].centroid =
diff --git a/src/compiler/glsl/builtin_variables.cpp b/src/compiler/glsl/builtin_variables.cpp
index d20fc4a816c..4e2de37fbba 100644
--- a/src/compiler/glsl/builtin_variables.cpp
+++ b/src/compiler/glsl/builtin_variables.cpp
@@ -323,6 +323,7 @@ per_vertex_accumulator::add_field(int slot, const glsl_type *type,
    this->fields[this->num_fields].name = name;
    this->fields[this->num_fields].matrix_layout = GLSL_MATRIX_LAYOUT_INHERITED;
    this->fields[this->num_fields].location = slot;
+   this->fields[this->num_fields].offset = -1;
    this->fields[this->num_fields].interpolation = INTERP_QUALIFIER_NONE;
    this->fields[this->num_fields].centroid = 0;
    this->fields[this->num_fields].sample = 0;
diff --git a/src/compiler/glsl_types.cpp b/src/compiler/glsl_types.cpp
index c549230a83c..2421bd61954 100644
--- a/src/compiler/glsl_types.cpp
+++ b/src/compiler/glsl_types.cpp
@@ -120,6 +120,7 @@ glsl_type::glsl_type(const glsl_struct_field *fields, unsigned num_fields,
       this->fields.structure[i].name = ralloc_strdup(this->fields.structure,
                                                      fields[i].name);
       this->fields.structure[i].location = fields[i].location;
+      this->fields.structure[i].offset = fields[i].offset;
       this->fields.structure[i].interpolation = fields[i].interpolation;
       this->fields.structure[i].centroid = fields[i].centroid;
       this->fields.structure[i].sample = fields[i].sample;
@@ -159,6 +160,7 @@ glsl_type::glsl_type(const glsl_struct_field *fields, unsigned num_fields,
       this->fields.structure[i].name = ralloc_strdup(this->fields.structure,
                                                      fields[i].name);
       this->fields.structure[i].location = fields[i].location;
+      this->fields.structure[i].offset = fields[i].offset;
       this->fields.structure[i].interpolation = fields[i].interpolation;
       this->fields.structure[i].centroid = fields[i].centroid;
       this->fields.structure[i].sample = fields[i].sample;
@@ -880,6 +882,9 @@ glsl_type::record_compare(const glsl_type *b) const
       if (this->fields.structure[i].location
           != b->fields.structure[i].location)
          return false;
+      if (this->fields.structure[i].offset
+          != b->fields.structure[i].offset)
+         return false;
       if (this->fields.structure[i].interpolation
           != b->fields.structure[i].interpolation)
          return false;
diff --git a/src/compiler/glsl_types.h b/src/compiler/glsl_types.h
index 2f612d8857d..b0e6f3f730f 100644
--- a/src/compiler/glsl_types.h
+++ b/src/compiler/glsl_types.h
@@ -837,6 +837,14 @@ struct glsl_struct_field {
     */
    int location;
 
+   /**
+    * For interface blocks, members may have an explicit byte offset
+    * specified; -1 otherwise.
+    *
+    * Ignored for structs.
+    */
+   int offset;
+
    /**
     * For interface blocks, the interpolation mode (as in
     * ir_variable::interpolation).  0 otherwise.