diff --git a/runtime/lua/vim/diagnostic.lua b/runtime/lua/vim/diagnostic.lua
index b42eece4c2..3321b6ad71 100644
--- a/runtime/lua/vim/diagnostic.lua
+++ b/runtime/lua/vim/diagnostic.lua
@@ -371,6 +371,39 @@ local function to_severity(severity)
   return severity
 end
 
+--- @param severity vim.diagnostic.SeverityFilter
+--- @return fun(vim.Diagnostic):boolean
+local function severity_predicate(severity)
+  if type(severity) ~= 'table' then
+    severity = assert(to_severity(severity))
+    ---@param d vim.Diagnostic
+    return function(d)
+      return d.severity == severity
+    end
+  end
+  if severity.min or severity.max then
+    --- @cast severity {min:vim.diagnostic.Severity,max:vim.diagnostic.Severity}
+    local min_severity = to_severity(severity.min) or M.severity.HINT
+    local max_severity = to_severity(severity.max) or M.severity.ERROR
+
+    --- @param d vim.Diagnostic
+    return function(d)
+      return d.severity <= min_severity and d.severity >= max_severity
+    end
+  end
+
+  --- @cast severity vim.diagnostic.Severity[]
+  local severities = {} --- @type table<vim.diagnostic.Severity,true>
+  for _, s in ipairs(severity) do
+    severities[assert(to_severity(s))] = true
+  end
+
+  --- @param d vim.Diagnostic
+  return function(d)
+    return severities[d.severity]
+  end
+end
+
 --- @param severity vim.diagnostic.SeverityFilter
 --- @param diagnostics vim.Diagnostic[]
 --- @return vim.Diagnostic[]
@@ -378,37 +411,7 @@ local function filter_by_severity(severity, diagnostics)
   if not severity then
     return diagnostics
   end
-
-  if type(severity) ~= 'table' then
-    severity = assert(to_severity(severity))
-    --- @param t vim.Diagnostic
-    return vim.tbl_filter(function(t)
-      return t.severity == severity
-    end, diagnostics)
-  end
-
-  if severity.min or severity.max then
-    --- @cast severity {min:vim.diagnostic.Severity,max:vim.diagnostic.Severity}
-    local min_severity = to_severity(severity.min) or M.severity.HINT
-    local max_severity = to_severity(severity.max) or M.severity.ERROR
-
-    --- @param t vim.Diagnostic
-    return vim.tbl_filter(function(t)
-      return t.severity <= min_severity and t.severity >= max_severity
-    end, diagnostics)
-  end
-
-  --- @cast severity vim.diagnostic.Severity[]
-
-  local severities = {} --- @type table<vim.diagnostic.Severity,true>
-  for _, s in ipairs(severity) do
-    severities[assert(to_severity(s))] = true
-  end
-
-  --- @param t vim.Diagnostic
-  return vim.tbl_filter(function(t)
-    return severities[t.severity]
-  end, diagnostics)
+  return vim.tbl_filter(severity_predicate(severity), diagnostics)
 end
 
 --- @param bufnr integer
@@ -714,10 +717,18 @@ local function get_diagnostics(bufnr, opts, clamp)
     end,
   })
 
+  local match_severity = opts.severity and severity_predicate(opts.severity)
+    or function(_)
+      return true
+    end
+
   ---@param b integer
   ---@param d vim.Diagnostic
   local function add(b, d)
-    if not opts.lnum or (opts.lnum >= d.lnum and opts.lnum <= (d.end_lnum or d.lnum)) then
+    if
+      match_severity(d)
+      and (not opts.lnum or (opts.lnum >= d.lnum and opts.lnum <= (d.end_lnum or d.lnum)))
+    then
       if clamp and api.nvim_buf_is_loaded(b) then
         local line_count = buf_line_count[b] - 1
         if
@@ -771,10 +782,6 @@ local function get_diagnostics(bufnr, opts, clamp)
     end
   end
 
-  if opts.severity then
-    diagnostics = filter_by_severity(opts.severity, diagnostics)
-  end
-
   return diagnostics
 end