diff --git a/icu4c/source/i18n/double-conversion.h b/icu4c/source/i18n/double-conversion.h
index 6df68b66237..693ada407fa 100644
--- a/icu4c/source/i18n/double-conversion.h
+++ b/icu4c/source/i18n/double-conversion.h
@@ -280,7 +280,9 @@ class DoubleToStringConverter {
                    StringBuilder* result_builder) const;
 #endif // not needed for ICU
 
-  enum DtoaMode {
+// ICU PATCH: Export these as U_I18N_API for unit tests.
+
+  enum U_I18N_API DtoaMode {
     // Produce the shortest correct representation.
     // For example the output of 0.299999999999999988897 is (the less accurate
     // but correct) 0.3.
@@ -301,7 +303,7 @@ class DoubleToStringConverter {
   // kBase10MaximalLength.
   // Note that DoubleToAscii null-terminates its input. So the given buffer
   // should be at least kBase10MaximalLength + 1 characters long.
-  static const int kBase10MaximalLength = 17;
+  static const int U_I18N_API kBase10MaximalLength = 17;
 
   // Converts the given double 'v' to ascii. 'v' must not be NaN, +Infinity, or
   // -Infinity. In SHORTEST_SINGLE-mode this restriction also applies to 'v'
@@ -341,7 +343,7 @@ class DoubleToStringConverter {
   // terminating null-character when computing the maximal output size.
   // The given length is only used in debug mode to ensure the buffer is big
   // enough.
-  static void DoubleToAscii(double v,
+  static void U_I18N_API DoubleToAscii(double v,
                             DtoaMode mode,
                             int requested_digits,
                             char* buffer,
diff --git a/icu4c/source/i18n/i18n.vcxproj b/icu4c/source/i18n/i18n.vcxproj
index bcfb7d022f1..47592a44960 100644
--- a/icu4c/source/i18n/i18n.vcxproj
+++ b/icu4c/source/i18n/i18n.vcxproj
@@ -879,6 +879,14 @@
     <ClInclude Include="decNumber.h" />
     <ClInclude Include="decNumberLocal.h" />
     <ClInclude Include="digitlst.h" />
+    <ClInclude Include="double-conversion-bignum-dtoa.h" />
+    <ClInclude Include="double-conversion-bignum.h" />
+    <ClInclude Include="double-conversion-cached-powers.h" />
+    <ClInclude Include="double-conversion-diy-fp.h" />
+    <ClInclude Include="double-conversion-fast-dtoa.h" />
+    <ClInclude Include="double-conversion-ieee.h" />
+    <ClInclude Include="double-conversion-utils.h" />
+    <ClInclude Include="double-conversion.h" />
     <ClInclude Include="dt_impl.h" />
     <CustomBuild Include="unicode\dtfmtsym.h">
       <Command Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">copy "%(FullPath)" ..\..\include\unicode
diff --git a/icu4c/source/i18n/i18n.vcxproj.filters b/icu4c/source/i18n/i18n.vcxproj.filters
index c728d4c1397..bf7c9ec7e4b 100644
--- a/icu4c/source/i18n/i18n.vcxproj.filters
+++ b/icu4c/source/i18n/i18n.vcxproj.filters
@@ -725,6 +725,30 @@
     <ClInclude Include="digitlst.h">
       <Filter>formatting</Filter>
     </ClInclude>
+    <ClInclude Include="double-conversion-bignum-dtoa.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
+    <ClInclude Include="double-conversion-bignum.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
+    <ClInclude Include="double-conversion-cached-powers.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
+    <ClInclude Include="double-conversion-diy-fp.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
+    <ClInclude Include="double-conversion-fast-dtoa.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
+    <ClInclude Include="double-conversion-ieee.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
+    <ClInclude Include="double-conversion-utils.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
+    <ClInclude Include="double-conversion.h">
+      <Filter>formatting</Filter>
+    </ClInclude>
     <ClInclude Include="dt_impl.h">
       <Filter>formatting</Filter>
     </ClInclude>